Albert Barnes Commentary Matthew 26:17

"Now on the first [day] of unleavened bread the disciples came to Jesus, saying, Where wilt thou that we make ready for thee to eat the passover?" — Matthew 26:17 (ASV)

The first day, etc. The feast continued eight days, including the day on which the paschal lamb was killed and eaten (Exodus 12:15). That was the fourteenth day of the month Abib, corresponding to parts of our March and April.

Of unleavened bread. It was called this because, during those eight days, no bread made with yeast or leaven was allowed to be eaten. Luke says, when the Passover must be killed. (Luke 22:7). That is, the time when the paschal lamb, or the lamb eaten on the occasion, must be killed. The word in the original, translated "Passover," commonly means, not the feast itself, but the lamb that was killed on the occasion.

See Exodus 12:43; Numbers 9:11; John 18:28; and 1 Corinthians 5:7, where Christ, our Passover, is said to be slain for us; that is, our Paschal Lamb, so called on account of His innocence, and His being offered as a victim, or sacrifice, for our sins.