I'm a bit confused about which day the Passover happened: Thursday or Friday of Passion week, and just want to make sure that I'm understanding it correctly. On Thursday afternoon, the disciples were sent to request the upper room, and likely the lamb was slain that day. When sundown came, it was Friday (by a Jewish understanding), and the Passover was eaten at this time (correct?)...I guess the question enters in when reading John 18:28, clearly in the midst of Jesus' trials, when John writes that the Jews did not enter Pilate's Praetorium "in order that they might not be defiled, but might eat the Passover." This makes it sound like Passover was to be eaten Friday evening (or Saturday, by the Jew's understanding).
Here was my reply:
Jesus’ disciples must have sacrificed their lamb Thursday afternoon and eaten the meal together on Thursday night. Many other Jews went to the temple on Friday afternoon and ate their meal Friday at sundown. So the Lamb of God would have died just as thousands of lambs were being slaughtered in the temple.
There have been many proposed solutions to the discrepancy between John and the Synoptic gospels, but newer research seems to show two different nights that the Jews would celebrate the Passover meal.
Robert Thomas, in his Harmony of the Gospels, explains in detail:
The Jews of Jesus’ day apparently recognized a dual method of reckoning dates. In addition to the better known system which regarded each new day as starting at sundown, the policy of some was to reckon from sunrise to sunrise. Each of these customs finds support from the OT, the former in such places as Gen. 1:5 and Ex. 12:18 and the latter in Gen. 8:22 and 1 Sam. 19:11.
The system of reckoning used by Jesus and His disciples and described by Matt., Mark, and Luke was from sunrise to sunrise. John describes the events from the perspective of a sunset-to-sunset reckoning. Indications are that the difference in systems was also a point of disagreement between the Pharisees (sunrise to sunrise) and the Sadducees (sunset to sunset).
The synoptic accounts therefore see Jesus as eating a Passover meal the evening before His crucifixion. For those who followed the sunrise-to-sunrise reckoning, the Passover lambs had been slain a few hours earlier, in the afternoon. For them the slaughter took place on the 14th of Nisan, as did the Passover meal. The 15th did not begin until the next morning, Friday, at about 6:00.
The Johannine description, however, views the events from the standpoint of the Sadducees who controlled the Temple. Jesus was crucified at the normal time of killing the Passover lambs, that is, the afternoon of Nisan 14. Nisan 14 had begun at sunset Thursday and would not end until sunset Friday. This was the normal time for the lambs to be slain, but the Temple authorities had apparently compromised with those who followed the other calendar and allowed them to slay the lambs on Thursday afternoon. This difference explains why Jesus’ accuser had not yet eaten the Passover (Jn. 18:28). They were about to do it Friday evening, Nisan 15, which began at sunset.
If the above solution is correct (and it is impossible at this point to say dogmatically that it is, but it does seem to handle all the data more effectively than other proposals), then Jesus was crucified on Nisan 15 according to the sunrise-to-sunrise reckoning and on Nisan 14 according to the sunset-to-sunset method. (appendix 10, pp. 321-22)
Peter Walker hints at this also in In the Steps of Jesus:
There are clear suggestions in John’s Gospel…that Jesus’ crucifixion took place during Nisan 14 (not 15) – around the time when the Passover lambs were being slaughtered in the nearby Temple.
That may be part of John’s point (Jesus, he was implying, was now the true Passover lamb). Yet it would also have made sense historically for Jesus to celebrate it 24 hours early. Conceivably this altered schedule brought Jesus into line with other Jewish groups (the Essenes or Pharisees), who may have been operating on different calendars. Yet the main reason may have been starkly practical: Jesus knew that, if he waited another 24 hours, it would be too late. He would be dead. (p. 156)
At our church’s last communion service, I preached on 1 Corinthians 5:7 and found this whole connection between Christ and Passover to be quite amazing. Down to the tiniest detail, our Lord pointed to the importance and blessing of His substitutionary death.