SCRIPTURE COMMENTARY #483And taking bread, he gave thanks and brake and gave to them, saying: "This is my body, which is given for you. Do this for a commemoration of me." In like manner, the chalice also, after he had supped, saying: "This is the chalice, the new testament in my blood, which shall be shed for you." (Luke 22:19-20)
THE TRUE PASCHAL LAMB: Now you can understand why our Lord instituted the Blessed Sacrament immediately after the Paschal feast. The Jewish Paschal lamb was the most perfect type of the Blessed Sacrament. Our Lord first ate the typical Paschal lamb, and by so doing closed the Old Testament: having done so, He instituted the Blessed Sacrament, the true Paschal Feast, and with it instituted the New Testament of grace: thus at the Last Supper we see shadow and substance together, type and anti-type. Jesus Christ, in the Blessed Sacrament, is our Paschal Lamb, because He first sacrifices Himself for us, and then gives Himself to us as our Food; and it is for this reason that the words: "Lamb of God, who takest away the sins of the world, have mercy on us," are said in the Mass just before the priest's Communion. The Jewish Paschal lamb was sacrificed and eaten first as a means and then as a memorial of the deliverance from the bondage in Egypt: our Paschal Lamb is sacrificed and eaten as a perpetual means and memorial of our deliverance from the slavery of sin and Satan, and in thanksgiving for the grace of Redemption.
[From 'A Practical Commentary on Holy Scripture' by Bishop Knecht, D.D.]
(1899 Douay-Rheims Bible)