Luke 22:7

The Jews slew their Passover lamb on the fourteenth of Nisan and ate it after sundown. Sundown began the fifteenth. The fourteenth would have been Thursday until sundown. This verse marks the transition to Thursday from Wednesday, the day on which Jesus had His controversy with the leaders in the temple and gave the Olivet Discourse. This is another of Luke’s benchmarks that signals Jesus’ relentless movement toward the Cross.

Luke evidently referred to this day as the day of unleavened bread because it was the first day of the combined feasts of Passover and Unleavened Bread. The Jews referred to the whole period as the feast of Unleavened Bread sometimes and as the Passover sometimes (cf. Luke 2:42; Luke 22:1; Acts 12:3-4). Another possibility is that this was the day on which they removed all leaven from their homes in preparation for the Passover. [Note: Morris, p. 304.]