There has been a long standing debate over the meaning of Matthew 12:40, “for just as Jonah was three days and three nights in the belly of the sea monster, so shall the Son of Man be three days and three nights in the heart of the earth.” In my opinion, the evidence supports the traditional view that Jesus was crucified on Friday afternoon and was in the grave part of Friday (the day of preparation cf. Luke 23:54-55), all of Saturday (Luke 23:56), and part of Sunday, the first day of the week (Luke 24:1). Some of the evidence for this is as follows:
(1) To us, three days and three nights generally means 72 hours, but we must understand the Bible historically and culturally. For the Jewish mind, this could mean any part of the first day, all of the second day, and any part of the third day. This is obvious by comparing Esther 4:16 and 5:1. Esther mentioned fasting for three days and nights and said that she would then go into the king, which she did, but 5:1 tells us clearly that it was on the third day that she went into the king, not after three days or on the fourth. This simply illustrates the way the Jews reckoned time.
(2) Further, the statement “after three days” could mean to the Jewish mind “on the third day” since any part of that day was considered the third day (cf. Matt. 27:63-64). Note the statements, “after three days” and securing the tomb until the third day. More will be said on this below.
(3) But on the third day could not mean on the fourth day, i.e., after a full 72 hours. Compare Luke 24:1 with 24:21. We read that they arrived at the tomb “on the third day” and then in verse 21 it is stated that “it is the third day.” This would be impossible to say if Jesus had stayed in the tomb for a full 72 hours for it would then be the fourth day. His resurrection would have had to be after the third day and on the fourth.
(4) Also, “the day of preparation” (Luke 23:54) could only refer to Friday before the Sabbath since no work of any kind could be done on the Sabbath, the seventh day. On other Sabbaths, holy days, domestic work could be done like making fire and cooking. No special preparation was needed for those Sabbaths or holy days, but not so on “the High Sabbath.” We might also note that the “day of preparation,” the Greek paraskeue, means Friday in modern Greek. See Ex. 16:22-23. The point here is that Friday is the only day a preparation day was needed as a preparation for the Sabbath, our Saturday.
(5) In several passages (the majority, about 4-1) it is said Jesus would rise “on the third day.” If the resurrection occurred after a full 72 hours (3 days) it would have been on the fourth. Compare Matt. 16:21; 17:23; 20:19; Luke 24:7, 21, 46; 1 Cor. 15:4. See below also regarding the use of the dative case here.
(6) In my mind, comparing all that is said in Luke 23:54-24:1 and John 19:31, settles the issue because of the day of preparation, Friday, being needed to prepare for a special high day or high Sabbath along with the fact the women came to the tomb on Sunday morning which is described as the third day.
62 Now on the next day (i.e., the High Sabbath, Saturday), which is the one after the preparation (i.e., Friday), the chief priests and the Pharisees gathered together with Pilate, and said, “Sir, we remember that when He was still alive that deceiver said, ‘After three days I am to rise again.’ 64 “Therefore, give orders for the grave to be made secure until the third day, lest the disciples come and steal Him away and say to the people, ‘He has risen from the dead,’ and the last deception will be worse than the first.”
Note, they said, “until the third day, not until the fourth.” Matthew could have used a Greek construction here which would have stressed through (duration) the third day, but using the preposition eos with the genitive, it basically meant “till or up to” and does not stress the idea of duration meaning “through.” The genitive case typically stresses during, at, or within a time range. Had the accusative been used alone or with a different preposition, it could have stressed extent or duration of time.
It is probably significant that “Every occurrence of the ‘the third day’ with reference to Jesus’ resurrection in the Gospels is put in the dat. (dative case) without an accompanying preposition” (Dan Wallace, Greek Grammar Beyond the Basic, Zondervan, p. 156). The significance of this is that nouns used in the dative case like “the third day” express a point in time rather than duration of time. So it means, “at a point in time, on the third day.”