Part V: the offertory.

The priest ascends the altar, just as Christ ascended Calvary. He should do so in humility and devotion. Three steps to the altar, these should remind us of what the Sanctuary is: Sanctus, sanctus, sanctus. It is holy, for the thrice holy God dwells therein, and is worshiped therein.
The missal and the veiled chalice sit o the altar, where the servers have taken them, and the priest prepares the altar.
He opens the burse, and lays down the Corporal, a square white piece of linen set on the altar, on which the host, the chalice , the ciborium, and the monstrance at benediction. It so called because on it is laid the body of Christ, Corpus Cristi.
On it he places the ciborium, which holds the consecrated hosts, the Paten, and the Chalice.
He takes the paten holding the bread, and holds it at eye level saying:

"Benedíctus es, Dómine, Deus univési, quia de tua largitáte accépimus panem, quem tibi offérimus, fructum terræ et óperis mánuum hóminum:
ex quo nobis fiet panis vitæ"

"Blessed art thou, O Lord, God of all creation,
for we have received from the goodness of thine abundance
the bread we offer unto thee,
the fruit of the earth and work of human hands:
it will become for us the bread of life."

Just as Christ gave thanks to the father in offering the bread and wine at the last supper, so does the priest follow. (Luke 22:19-20) We pay thanks to God for his abundant giving to us, he gave us of his good will, the bread we offer, and gives us Christ as our food.This bread, made by men, lying on the altar will become the bread of life, the body, blood, soul, and divinity of Jesus Christ our lord. Now, it is common food, but it will become the bread of angels, come down from heaven. Abbe Durand says of the offering of the bread:

"The Offering of the Bread and Wine.—Like his divine Master, the priest takes bread in his hands and offers it to God. The bread here takes the place of the Church and Christian people, for, as bread is the nourishment and life of man, when he offers it at the altar it is as if he offered himself to God to be sacrificed to His glory, like Jesus Christ, our head. As the bread is to be changed into the body of Jesus Christ, may our hearts also be transformed into Him, till it may be " no more we who live, but Jesus Christ Who lives in us."
He places the paten on the altar.
The Offertory, or Preparation of the Offerings precedes the offering of the mass. In the offertory, the celebrating priest takes bread and wine, and offers them to God in the name of the people, praying that they will become the body and blood of Christ our God. He takes the chalice, and wipes any dust out of it with the purificator, A small linen cloth used to purify the sacred vessels, and the priest's fingers after the ablutions. He goes to the right side of the altar with the chalice, and pours wine into it. The, taking the cruet of water, he blesses it and pours a drop of water into the chalice saying:

"Grant that by the mystery of this water and wine
may we be made partakers in his divinity,
who humbled himself to share in our humanity."

This water, added to wine was originally done in the days of the persecution of the church, do dilute the wine so that it would not be strong enough to be smelt by those who persecuted the Christians.Now, it symbolizes:
1) The human and divine natures of Christ
2) Our redemption by blood ad water, flowing from the side of Christ.
3) Our share in the divine life , even as Christ shared our human life. All this is summed up in the prayer.

Taking the chalice to the center of the altar, he prays:

"Benedíctus es, Dómine, Deus univési,
quia de tua largitáte accépimus
vinum, quod tibi offérimus,
fructum vitis es óperis mánuum hóminum,
ex quo nobis fiet potus spiritális.

"Blessed art thou, O Lord, God of all creation
for we have received from the goodness of thine abundance
this wine we offer unto thee,
the fruit of the vine and work of human hands:
it will become for us the spiritual drink."

He prays that the wine, fruit of the vine, would become for us the blood of Christ, the drink of heaven, and chalice of salvation. That phrase, fruit of the vine comes from the gospel itself. (Luke 22:18) And it has a double meaning. The wine, the fruit of the vine will become the true fruit of the vine, the true spiritual drink, which is the precious blood. For who is the vine except Jesus, who said "I am the vine and you are the branches" ?
Dom Gueranguer says of the offering of the wine:

"Lord Jesus, who art the true Vine, and whose Blood, like a generous wine, has been poured forth under the pressure of the Cross! thou hast deigned to unite thy divine nature to our weak humanity"

Abbe Durand says of the offering of the wine:

"Our Lord also offered wine mixed with water. The wine represents Jesus Christ, "the true vine"; and water, the Christian people. St. Cyprian, in a letter to Cecilius, teaches this formally. This image is a vivid figure of the ineffable union of God with man wrought by the incarnation, and of that other union in the Eucharist, and again of that third union which will be consummated in glory. It is, then, the Church united with Jesus Christ, the members to their head, the bride to her bridegroom, which the priest offers to God in the oblation of the chalice.
In the drop of water, which is the figure of the faithful, what an admirable lesson of humility ! Is it not a striking image of our annihilation in the presence of the God of the Eucharist ?

While the priest offers the bread and wine to God, the offertory antiphon is chanted. Afterwards, the choir may sing a motet, or a hymn. We too, should offer ourselves to God during the offertory. We should offer him all our prayers and works and intentions, for the past week, and the week to come, and a sweet smelling savour to God.
Bowing down, the priest prays:

"In spiritu humilitatis, et in animo contrito
suscipiamur a te, Domine
et sic fiat sacraficium nostrum in conspectu tuo hodie,
ut placeat tibi, Domine."

"In a humble spirit, and with a contrite heart
may we be accepted by thee, O Lord,
and may our sacrifice so be offered to thee this day
as to be pleasing in thy sight, Lord God."

This prayer is related to to Daniel 3:39-40, part of the canticle said at Lauds in the breviary on Tuesdays. It's a good verse to read before mass, and we should pray it as part of our devotions during the offertory.It is easy to see why the early church, amidst the murder of her priests, bishops, and even the early popes, should take this verse as part of her worship during the offertory. She could have no public worship, no church buildings, and could not offer her worsip as she desired. Later, it developed into the prayer priests pray now.We should attend mass in humility, and humility should be our entire bearing while present. This is why we genuflect, and show so many signs of reverence in mass. humility is seeing yourself as you really are, and we really are sinful, and unworthy to partake of this sacrifice. This isn't Jansenism, it's the simply way of how things are.

Raising himself, he goes again to the right of the altar, and blessed incense with the sign of the cross. He incenses the gifts of God, to be offered to God, the cross, the reminder of Christ's sacrifice which is so soon to take place, and the altar itself, on which the sacrifice takes place.
Finally, the celebrant himself is incensed and then the people, the gathered body of Christ.
He washes his hands saying the second verse of Psalm 50:

"Lava me, Domine, ab iniquitate mea,
et a peccatto meo, munda me."

"Wash me thoroughly,O Lord, from my iniquity
and cleanse me of my sin."

Originally, washing the hands was necessary after handling and incensing the offerings. Now we do it in remembrance of Christ's command to St.Peter at the first mass. (John 13:8)
If we are not clean interiorly, through the grace that comes from prayer, confession of our sins, and living a life with Christ, we shall have no part of him at the banquet of the lamb
.
The priest pauses at the center of the altar a bit, for prayer, and then turns to the people saying:

"Oráte, fratres:
ut meum ac vestrum sacrifícium
acceptábile fiat apud Deum
Patrem omnipoténtem."

'Pray, brethren
that the sacrifice which is mine and yours
may be acceptable to God
the almighty Father.'

we respond:

" Suspiat Dominum sacrificium de manibus tuis
ad laudem et gloriam nominis suis
ad utilitatem quoque nostram
totiusque Ecclesiae suae sanctae."

"May the Lord accept the sacrifice at your hands
for the praise and glory of his name,
for our good
and the good of all his holy Church."

These are three of the ends for which the mass is offered:
1) It gives glory to God
2) It is offered for our good.
3) It is offered for the state of all of God's holy church throughout the world.
The servers close the sanctuary gates.
The celebrant prays a short prayer called the 'super oblata', or 'prayer over the offerings.'
At the end, comes the dialogue and preface. The use of a dialogue and preface is an early custom of the church, going at least back to the time of St. Hyppolytus. In it, we give thanks to God the Father before the Eucharistic offering, just as Jesus gave thanks to the Father at the last supper before the Eucharistic offering. (Luke 22:19, 1 Cor. 11:23-25)
Then , we sing the Sanctus. A majestic hymn of praise to God, based on Isaiah 6:3,Psalm 118:26, and Mark 11:10.
Then we all kneel (Rev. 5:14.) for the Canon of the mass.