Good question! The Gospels do not record Peter and John going to the Temple to present a lamb for sacrifice, and while it isn't always safe to assume anything, it stands to reason if they were to Go and prepare the Passover for us... (Luke 22:8), it would incorporate all the details needed at that time. The Passover meal would be incomplete without the roasted lamb. I can see how some would have a hard time seeing Jesus partaking of a lamb if it was symbolic of His sacrificial death; yet, it was also a memorial of the Redemption of Israel. Up until this time, Jesus had been faithful to follow the Biblical (not Pharisee) injunctions imposed by the Law of Moses (two feast in particular - Passover and Tabernacles), and even a non-Biblical feast, the Feast of Dedication (Hanukkah).Among other things, Jesus was an observant Jew (His mother was Jewish).Jesus presented the Unleavened Bread as His broken body and there is rich symbolism here. Originally the unleavened bread symbolized the haste in which the meal was prepared but leaven became a symbol for the evil impulse of the heart. Unleavened bread became a symbol for freedom from decay, thus Jesus was prefiguring His resurrection and symbolically partake of His resurrection life.The eating of the Unleavened Bread and the Cup of Redemption became the focal point of the Gospel record. One pointing to the Resurrection Life sustained by ingesting the anticipated Resurrection of Jesus (see Romans 6:1f), and the Blood ratification of the New Testament (See Exodus 24, where Moses uses similar, if not identical language, vv. 8; also the context of a fellowship meal in which Yahweh attended) The HammerMi kamocah ba'elim AdonaiWho is like you, Adonai, among the mighty? (Exodus 15:11