Understanding the Liturgy: The Offertory
The offertory, simply defined, is the rite of bringing the offerings of bread and wine into the Altar. This rite has undergone a process of evolution in churches all over the world. This evolution involved basically three stages. We have enough information that enables us to reconstruct these stages of development.
In the beginning:
In the very early Church, this rite was practiced after the kiss of peace. The first part of the Liturgy was known as the Liturgy of the catechumens (candidates for baptism). This was comprised of readings from the bible, the acts of the martyrs and a sermon by the Bishop, who normally presided at the Eucharist. The kiss of peace concluded this part of the Liturgy. The catechumens were asked to leave since they were not allowed to see the holy things which belong only to the holy (the faithful). This was in obedience to the Lord’s admonition “Cast not thy pearls before swine” (Matt. 7:6).
The doors of the church (or more probably, the house, where the Eucharist was celebrated) were then closed. The large veil that covered the altar (to conceal it from the eyes of the catechumens) would be removed by the priest and the deacon, and brought into the assembly. The deacon would then exhort the people in Greek saying, “Prospherin Kata etropon” (meaning, offer in order) and the people would then bring their offerings of bread and wine, putting the bread in the large veil. The deacon and the priest would then bring the offerings into the altar, where the Bishop, after washing his hands, starts the Liturgy of the faithful by saying. “The Lord be with you all.”
Traces of the old practices still remain in our liturgy and serve as telltales of the past. Even though the offertory has now been moved to the beginning of the Liturgy, the deacon still exhorts the people to offer by saying “Prospherin,” after they have exchanged the kiss of peace (the original time for the Offertory). The washing of hands has been moved with the offertory to the beginning of the mass, but is practiced again before the Liturgy of the faithful. The veil that covers the altar is still known as the “prospherin” even though it is no longer used to collect the “prosphora” (the gifts).
The great entrance:
About the time Constantine became Emperor, and the churches started to enjoy peace and prosperity, the simple rite of bringing the offerings to the altar gradually evolved into the elaborate “great entrance,” most probably of Byzantine origin. The rite was also moved to its present position; at the very beginning of the Liturgy, before the Liturgy of the catechumens. No longer would the people bring their gifts directly to the altar but rather give them to the deacons; ahead of time. The deacons and the priests, dressed in their beautiful vestments, with tapers lit, and censors in their hands, would then bring the offerings in a procession that starts from the door of the church and ends in the sanctuary.
There are three main reasons for the evolution of this rite. First, as more people entered the faith, it became impractical to let everyone bring in their gifts to the altar.
Second, the catechumens became mainly infants and the Church was not as obsessed with secrecy as in the beginning.
Third, the peace and prosperity brought about by Constantine’s edict allowed the building of churches that were suitable for this elaborate procession.
Traces of this practice survives in our Liturgy, for (the eves of) the three great feasts of the Nativity, Epiphany and Easter.
The contemporary rite:
The final stage of the evolution of the rite was a return to a less elaborate procession. Rather than circle the whole church, the priests and the deacons carry the gifts of bread and wine, circling the altar instead (see the procession of the Lamb, later).
Although less elaborate from the outside, the rite has become laden with complex rituals that are full of symbolism concerning the death and burial of our Lord. The death of our Lord had many Old Testament “types,” or symbols. The oldest symbol was the immolation of the “Passover Lamb”. John the Baptist called Christ “the Lamb of God that taketh away the sin of the world” (John 1:29). Saint Paul also refers to Christ as “our Passover” (1Cor. 5:7). That is why we call the bread of the oblation “the lamb” and the circling of the gifts around the altar, “the procession of the Lamb.”
After the Psalms are concluded, the priest stands at the door of the sanctuary, facing the west. The bread and wine are presented to him while a deacon stands at his right carrying a veil in his right hand and a lighted taper in his left hand. The priest would then examine the loaves of the bread to choose “a lamb without blemish” (Ex. 12:5, 1 Pet. 1:19). He also examines the wine, making sure it has not gone sour, then gives it to the deacon standing at his right. The priest would then bring in the chosen “lamb” and puts it on a veil setting it down on the north side of the altar. The deacon would bring the wine into the sanctuary.
The entrance of the gifts into the sanctuary is a symbol of the entrance of Christ who, “By His own blood ÿ entered in once into the holy place, having obtained eternal redemption for us” (Heb. 9:12).
Christ’s entrance into the holy place to offer himself “without spot to God” (Heb. 9:14), was prefigured in the Old Testament not only by the Paschal lamb (Ex. 12:5), but also by the high priestly sacrifice of the day of atonement (Yum Kippur) (Ex. 30:10, Heb. 9:7). The rubric reminds us of these two Old Testament figures. The Paschal lamb figure is the reason the “bread” chosen by the priest is henceforth called simply the “Lamb.” The symbolism of the day of atonement sacrifice will be dealt with later in detail.
The washing of hands:
The priest would then wash his hands three times. This no doubt is related to the ablutions that the Old Testament priests were required to do before immolating the sacrifices in the temple. These washes, which to the Jews meant ritual purity, have now acquired a new meaning. Saint Cyril of Jerusalem (fourth century) explains it this way:
You saw, then, the deacon who offers the water for the washing of the hands of the celebrant and to the presbyters who encircle the altar of God. Not that he offered this water on account of any bodily uncleanness, for we did not enter the church unwashed; rather the ablution is a symbol of our obligation to be clean from all sins and transgressions. The hands symbolize action. So by washing them we signify plainly the purity and blamelessness of our conduct. Did you not hear the blessed David explaining the mystery of this ceremony when he says, “I will wash my hands among the innocent and will circle your altar, O Lord” (Ps. 25:6) 
The Psalm alluded to by Saint Cyril is actually recited by the priest as he washes his hands. Note also how he sees in this psalm an explanation not only of the washing of the hands but also of the circling of the altar (the procession of the Lamb) that follows it.
The rubric then directs the priest to dry his hands slightly, and then carrying the Lamb on the palm of his left hand, he rubs it above and below with his right hand, while saying this prayer, “Grant O Lord that our sacrifice may be accepted in Thy sight for my sins and for the ignorances of Thy people ÿ ”
The words of the priest bring to our mind the Old Testament sacrifice of the day of atonement, when, once a year, the high priest would enter the holy of holies, “not without blood, which he offered for himself and for the people’s sins committed in ignorance” (Heb. 9:7, Lev. 16). The priest is thus signifying that the imperfect sacrifice of the Old Testament has now been replaced by the perfect sacrifice of Christ, Who himself has become our sin offering. (Is. 53:10)
In the Old Testament sacrifice of the day of atonement, as in other sin sacrifices, the high priest had to lay his hands on the sacrificial animal, then make an atonement for himself and for the sins the people committed in ignorance. The laying on of hands signifies transfer of the sins to the sacrificial animal. The animal is then killed. Rubbing the Lamb may represent the old Testament’s laying on of hands,  while uttering the words, “Grant O Lord that our sacrifice may be accepted in Thy sight for my sins and for the ignorance of Thy people ÿ ” reminds us of the atonement that the high priest made for his own sins and for the sins the people made in ignorance.
After rubbing the lamb with his slightly wet hands above and below, the priest wraps it in a veil, and proceeds with the “Procession of the Lamb.” This action may be,
ÿ in imitation of the burial of Christ, wherein Joseph, after taking His body down from the Cross, wrapped it in clean linen after he had anointed it with spices and ointment, and carried it with Nicodemus, and buried it in the new tomb cut from the rock. 
So, the action of rubbing the Lamb (above and below with the slightly wet right hand of the priest), signifies, not only the laying on of hands, as done by the high priest in the Old testament, but also the anointing of the body of the Lord before being wrapped in linen, as recorded in the Gospel. (John 19:40)
The procession of the Lamb:
The priest then carries the lamb wrapped in a veil above his head. The deacon similarly wraps the wine flask in a veil, carries it above his head and follows the priest. The rubric directs that before each of them goes a deacon carrying a lighted taper. They all follow in a procession around the altar.
The procession around the altar would now be a symbol for carrying the body of Jesus wrapped in linen to lay it in the tomb. The priest and the deacon represent Joseph and Nicodemus who carried the body of our Lord. The deacons who precede them (carrying tapers), represent the two angels “who came and stood by throughout the passion and death of our Lord.”  These were the same angels whom Mary Magdalene saw in the empty tomb (John 20:12). The whole procession of the Lamb becomes a beautiful icon for the short journey from Calvary to the nearby sepulcher.
As the priest starts circling the altar he gives glory to God by saying this doxology, “Glory and honour, honour and glory unto the all holy Trinity, the Father, the Son and the Holy Spirit ÿ ” Then he asks God to give peace and edification (building up) to His Church that is now assembled and is kneeling in worship and reverence to the memorial of the passion of Christ.  Then he mentions those who brought the gifts, those on whose behalf they have been brought (the person in whose name the oblation is offered,) and those by whom they have been brought: probably the deacons who became “the guardians of the gifts brought by the people.” 
The day which the Lord has made:
The people respond by singing a psalm: usually part of Psalm 116. The Church always saw in this Psalm a reference to the day which the Lord hath made, Sunday, the day of the resurrection. That is why this hymn is sung only on Sundays, and especially on Easter Sunday. “This is the day the Lord has made, let us be glad and rejoice in it.”
Just as the Virgin Mary, Mother of God, holds first place among all women, so among all other days this day is mother of all ÿ This day is one of seven and one outside of seven ÿ This is the day the synagogue ended and the Church began ÿ For all these reasons, dearly beloved, let us chant in unison, “This is the day the Lord has made; let us rejoice and be glad in it.” 
The “signing” of the Lamb:
When the procession around the altar is concluded, the priest stands in front of the altar facing east. He puts the Lamb in the palm of his left hand, the deacon, holding the wine flask in his right hand (on a veil) with a lighted taper in his left hand, would then bring the wine closer to the Lamb. The priest makes the sign of the cross on both the bread and the wine three times, consecrating them in the name of the Father, the Son and the Holy Spirit. With the first signing he says, “Blessed be God the Father the Pantocrator;” in the second he says, “Blessed be His only begotten Son Jesus Christ Our Lord;” and in the third he says, “Blessed be the Holy Spirit the Paraclete.” In doing so, the priest starts the process of consecration of the gifts which involves signing them twenty seven times throughout the Liturgy.
The deacon responds after each signing by saying “Amen,” then he responds to the priest’s doxology by saying, “One is the Holy Father, One is the Holy Son, One is the Holy Spirit ÿ ” He then sings his own doxology, “Blessed be the Lord God forever. Amen.” Finally, he asks the congregation to share in glorifying the Lord God, by reciting Psalm 117: “Praise the Lord all ye nations, praise Him all ye people, for His mercy is confirmed upon us and the truth of the Lord endureth forever.” To this, the people respond by singing their own doxology, “Glory be to the Father and to the Son and to the Holy Spirit, Now and always and unto the ages of all ages. Amen.”
Now to understand all of this let us consider the deacon’s exhortation, “Praise the Lord all ye nations”. The Coptic, “ni ethnos tiro,” is often translated “all ye gentiles;” and indeed, when St. Paul quotes this psalm he uses the word gentiles (Rom. 15:11). This invitation to the gentiles to glorify God, at the beginning of the consecratory process of the gifts fulfills a very important prophesy in the book of Malachi, where the Lord says, “For from the rising of the sun even unto the going down of the same my name shall be great among the gentiles and in every place incense shall be offered unto my name and a pure offering.” (Mal. 1:11).
That the pure offering in this prophesy refers to the sacrifice of the Eucharist is quite obvious in the writings of the early Church Fathers. Justin Martyr comments on this prophesy saying,
In this passage God already speaks of the sacrifices which we, the gentiles offer Him in every place, namely the bread of the Eucharist and the cup, likewise, of the Eucharist. He foretells that we glorify His Name. 
So, we, the gentiles fulfill Malachi’s prophesy, by glorifying God. We glorify Him “for his mercy is confirmed upon us,” now that our offering (prosphora) has become “acceptable, being sanctified by the Holy Spirit” (Rom 15:16). We glorify Him for “His truth endureth forever”, since what He foretold of old, concerning the offering of the Gentiles, has been fulfilled, today, in our sight.
The Burial of the Lamb:
The priest now takes the bread and places it on a veil, which sits inside the paten. He also pours the wine into the chalice, mixing it with some water. The pouring of the wine is again, a symbol of the pouring of the blood of Christ. 
Then He says the Prayer of thanksgiving at the end of which is an inaudible prayer called the Prayer of the Prothesis:
Master, Lord Jesus Christ, the Co_eternal Logos of the unblemished Father, who art of one essence with Him and the Holy Spirit. For Thou art the Living Bread which came down from heaven, and didst afore time make Thyself a Lamb without spot for the life of the world. We ask and entreat Thy goodness O Lover of Mankind, show Thy face upon this bread, and upon this cup which we have set upon this, Thine holy table.
Now the priest makes the sign of the cross on the bread and the wine three times, while he says,
Bless them, sanctify them, purify them and change them, in order that this bread may become indeed Thine holy Body, and the mixture which is in this cup, indeed your precious blood. May they become for all of us a partaking, healing and salvation of our souls, our bodies and our spirits.
As usual, he ends the prayer with a doxology glorifying the Holy Trinity.
This prayer, sometimes called “pre-epiclesis,” marks a further step in the process of sanctifying the gifts, which starts at the offertory and finds its fulfilment in the Epiclesis.
The priest then covers the bread with a veil and the chalice with another veil. Then the priest and the deacon cover the altar with the Prospherin, and put another veil on top of the Prospherin.
Each one of these actions has a symbol that pertains to the burial of our Lord. The altar is a symbol of the tomb; the paten symbolizes the bier; the bread is the body of our Lord; the veil under the bread is the burial cloth, while the veil covering the bread stands for the cloth which was upon the head and face of Christ (John 20:7). The four hands of the asterisk “hugging” the bread in the paten, symbolize the hands of Joseph and Nicodemus who carried the body of Christ and laid it in the tomb. The prospherin becomes the stone that closed the door of the tomb and the triangular veil on top of it becomes the seal which was put on the stone. 
In case you wonder why there is this obsession with the death and burial and how it is related to the Eucharist, consider what the Lord said to His disciples: “For every time you eat of this bread and drink of this cup, you proclaim my death, confess my resurrection and remember me till I come.” The Church, the bride of Christ, has remained faithful to His command by proclaiming His death in the rites of the offertory, and confessing His resurrection in the lifting up of the Prospherin before the Anaphora. Did not the Lord command us saying, “do this in remembrance of me?” Can there be a better way of commemorating His holy passion, his resurrection from the dead – than re_enacting these life_giving actions by entrenching them in our Eucharistic rites?