This passage contains a couple of points to help us understand why Jesus Christ's death took place late on the afternoon of Abib 14, while the Passover was commanded to be observed at the beginning of that day. The first is that the entire sacrificial system, the Aaronic priesthood, and the Tabernacle system of worship were only copies of a spiritual reality. While the instructions given in the Pentateuch about these things are decidedly important in their own right—including the Passover instructions—they point to something that is vastly more significant. The physical rites were critically important for what God was doing with a carnal people, and they still contain valuable principles for us, but they in no way supersede the spiritual, heavenly reality.
Secondly, Jesus perfectly fulfilled all the spiritual requirements on which these physical rites were based. But it is imperative to remember that what was most important is what needed to be accomplished spiritually. The Father and the Son determined what needed to happen to meet the spiritual requirements. This passage shows that the Father was perfectly satisfied with everything that Jesus did, thus whatever the spiritual requirements were for the various sacrifices and rituals, they have been met. Everything in the sacrificial system that was of consequence to God's plan and His sense of justice has been fulfilled.
Yet, even though the physical rites point to the spiritual reality, they do not match up exactly. For example, the Israelites were required to make a morning sacrifice and an evening sacrifice. There is no doubt that Jesus Christ fulfilled all sacrificial requirements, including those. However, He was not crucified in the morning nor in the evening when those sacrifices were supposed to be made. He was not killed on a Sabbath, when special sacrifices were made. Nor was He killed on a new moon, when other special sacrifices were made. (The 14th day of the month is a full moon.)
Taking this a step further, the Day of Atonement is considered the holiest and most solemn day of the year. Only then could the high priest enter the Holy of Holies. The blood sacrifices for the sins of the priest and the nation were very detailed. In the passage above, Christ's sacrifice is described in the imagery of the Day of Atonement, not of the Passover. Jesus, though, was not sacrificed on Atonement. His blood was never sprinkled on any altar, let alone the Mercy Seat. Our High Priest did not enter the Holy of Holies of the physical Temple. He entered the heavenly Temple, but if He did that when He ascended to the Father, He did not do even that on the Day of Atonement.
Clearly, the way that Christ fulfilled all of these things was not identical to the requirements He gave to Israel. Rather, the instructions given to them were only types of what He would later fulfill in His life, crucifixion, and death.
David C. Grabbe
Why Was Jesus Not Crucified as Passover Began? (Part One)