Lambs were animals used as sacrifice for sins. The blood of the lamb was offered to God in atonement for our sins. Jesus was the final and complete sacrifice that atones for our sins. He is the Lamb sent from God.
This is why it is important that we reflect on the words of John the Baptist and the words we hear at every Mass: “Behold the Lamb of God, behold him who takes away the sins of the world. Blessed are those called to the supper of the lamb.”
The Holy Mass is where the Lord invites us to share in his Lamb. The lamb that truly does take away the sins of the world. Through reception of the Body of Christ our desire to do evil is lessened and we are united with Jesus Christ, our hope for eternal life.