22:7-18 Christ kept the ordinances of the law, particularly that of the passover, to teach us to observe his gospel institutions, and most of all that of the Lord's supper. Those who go upon Christ's word, need not fear disappointment. According to the orders given them, the disciples got all ready for the passover. Jesus bids this passover welcome. He desired it, though he knew his sufferings would follow, because it was in order to his Father's glory and man's redemption. He takes his leave of all passovers, signifying thereby his doing away all the ordinances of the ceremonial law, of which the passover was one of the earliest and chief. That type was laid aside, because now in the kingdom of God the substance was come.See this passage explained in the Matthew 26:17-19 notes, and Mark 14:12-16 notes. Lu 22:7-38. Last Passover—Institution of the Supper—Discourse at the Table.

7. the day of unleavened bread—strictly the fifteenth Nisan (part of our March and April) after the paschal lamb was killed; but here, the fourteenth (Thursday). Into the difficult questions raised on this we cannot here enter.

See Poole on "Luke 22:3"

And they said unto him, where wilt thou that we prepare? Meaning, not in what village, town, or city, for it was a fixed and determined thing, that the passover should be eaten at Jerusalem, and nowhere else; see Deuteronomy 16:2, but in what house in Jerusalem? And they said unto him, Where wilt thou that we prepare?