1 Corinthians 1:1-3
Jesus speaks through the prophet Isaiah in today's First Reading.
He tells us of the mission given to Him by the Father from the womb: "'You are My servant,' He said to Me."
Servant and Son, our Lord was sent to lead a new exodus —to raise up the exiled tribes of Israel, to gather and restore them to God. More than that, He was to be a light to the nations, that God's salvation may reach to the ends of the earth (see Acts 13:46-47).
Before the first exodus, a lamb was offered in sacrifice and its blood painted on the Israelites' door posts. The blood of the lamb identified their homes and the Lord "passed over" these in executing judgment on the Egyptians (see Exodus 12:1-23,27).
In the new exodus, Jesus is the "Lamb of God," as John beholds Him in the Gospel today (see 1 Corinthians 5:7; 1 Peter 1:18-19). Our Lord sings of this in today's Psalm. He has come, He says, to offer His body to do the will of God (see Hebrews 10:3-13).
The sacrifices, oblations, holocausts, and sin-offerings given after the first exodus had no power to take away sins (see Hebrews 10:4). They were meant not to save but to teach (see Galatians 3:24). In offering these sacrifices, the people were to learn self-sacrifice—that they were made for worship, to offer themselves freely to God and to delight in His will.
Only Jesus could make that perfect offering of himself. And through His sacrifice, He has given us ears open to obedience, made it possible for us to hear the Father's call to holiness, as Paul says in today's Epistle.
He has made us children of God, baptized in the blood of the Lamb (see Revelation 7:14). And we are to join our sacrifice to His, to offer our bodies—our lives—as living sacrifices in the spiritual worship of the Mass (see Romans 12:1).