Any or all of these elements could have been in John's mind as he pointed out Yeshua to those who had become his own followers. But one of those followers--also named John--recounted the Baptizer's declaration at the beginning of his Gospel in order to introduce a subtle theme, one which would crescendo on the day of Yeshua's crucifixion. Yeshua would be the ultimate Passover Lamb, the initiatory sacrifice of the final Redemption even as the original Passover sacrifice had initiated the first redemption from Egypt and became the archetype of the entire sacrificial system.
The first three Gospels clearly portray the final meal eaten by Yeshua and the twelve in the upper room on the eve of Yeshua's arrest as the Passover Seder (Mt. 26:17; Mk. 14:12; Lk. 22:7, 15). Just as clearly, John's Gospel seems to place that final meal prior to the actual celebration of Passover. John 13:1-2 tells us that the meal was held "before the Feast of the Passover" and, in fact, John's description of the upper room gathering makes no mention of the elements of the Passover Seder. In addition, John reports that the Chief Priests refused to enter Pilate's headquarters on the following day "so that they would not be defiled but might eat the Passover" (18:28). John also refers to that day--the day of Yeshua's crucifixion--as "the day of preparation for the Passover" (19:14), in other words, the 14th of Nisan on which the Seder would only later be eaten.
Interestingly enough, Jewish tradition (Babylonian Talmud, Sanhedrin 43a) indicates that Yeshua "was hanged [i.e. on the cross] on Passover eve." One manuscript of the Talmud from Florence even adds "on the eve of the Sabbath," providing a double confirmation of the day.
Many suggestions have been made to resolve the apparent contradiction between the accounts of the Synoptic Gospels (Matthew, Mark, and Luke) on the one hand, and that of John on the other. Often such attempts focus on reconciling John's account to the others by reinterpreting the verses cited above (see the NIV Study Bible notes, for example). More likely, however, John simply followed a different--Judean--dating system, one used by the Temple priesthood with whom John had personal connections (John 18:15), while the other Gospels followed a Galilean tradition of dating, which was only natural for Yeshua and his Galilean disciples, according to which the Seder fell one day earlier, i.e. Thursday evening. [For more information on the identification of the Last Supper, see Harold Hoehner, Chronological Aspects of the Life of Christ, Zondervan, 1977).
The greater question, however, is: why John did play down the identification of the Last Supper--in which he was an active participant--with the Passover Seder? As a Galilean, he certainly recognized Yeshua's celebration of the Passover on Thursday night as a legitimate Jewish option. What purpose was served by employing a different reckoning of the day and drawing attention to that reckoning in his account of Yeshua's final days?
In fact, from the opening presentation of the "Lamb of God," Yeshua's Passover ministry is a recurring theme in John's Gospel. But it is in the closing chapters of his Gospel that John brings these scattered rays of light into focus on the person of Yeshua on the cross. According to John, Yeshua was tried and condemned at the break of day on the eve of the Passover (19:14) and led off to be crucified later that morning. That afternoon, "between the evenings" (from 3:00-5:00PM; Mishnah Pesachim 5:1), the priests would be busy in the temple slaughtering the multitude of Passover lambs required for those who would celebrate the feast that night in the city, including the chief priests themselves (18:28). Just as they began their work, Yeshua, the Passover Lamb of God, was using his final breath to proclaim, "It is finished!" (19:30; cf. Mark 15:34-37, "the ninth hour" being 3:00PM in the Synoptics).
With the combined Passover-Shabbat rapidly approaching, the Jewish leaders sought to speed the death of those crucified by having their legs broken, so that they could be buried before the "entrance of the Sabbath" (John 19:31-32). The two revolutionaries executed along with Yeshua suffered this final indignity, but Yeshua himself was exempted, having already died. Surprisingly, John notes: "For these things came to pass to fulfil the Scripture, 'Not a bone of him shall be broken" (19:36).
Search the Scriptures and you will not find a single Messianic prophecy making this prediction. The detailed descriptions of Messiah’s sufferings in Isaiah 53 and Psalm 22 apparently miss this fact, which is based not on prophetic insight but on the detailed instructions concerning the original Passover lamb, concerning which we were instructed, "you are not … to break any bone of it" (Exodus 12:46).
But, far from misappropriation of Scripture, John sees in this small detail the hand of the Sovereign God, who so orchestrated both the times and seasons, along with the actions of hostile and ignorant men, that He might thereby reveal the true significance of Yeshua's sacrifice. This fact, noted only by John, is the final confirmation that Yeshua is indeed the ultimate Passover Lamb, bringing through his death the final Redemption to Israel and to the world.