From ADAM Clark Commentary

Matthew 12:40 Three days and three nights] Our Lord rose from the grave on the day but one after his crucifixion: so that, in the computation in this verse, the part of the day on which he was crucified, and the part of that on which he rose again, are severally estimated as an entire day; and this, no doubt, exactly corresponded to the time in which Jonah was in the belly of the fish. Our Lord says, As Jonah was, so shall the Son of man be, &c. Evening and morning, or night and day, is the Hebrew phrase for a natural day, which the Greeks termed nuxyhmeron, nuchthemeron. The very same quantity of time which is here termed three days and three nights, and which, in reality, was only one whole day, a part of two others, and two whole nights, is termed three days and three nights, in the book of Esther: Go; neither eat nor drink THREE DAYS, NIGHT or DAY, and so I will go in unto the king: Es 4:16. Afterwards it follows, Es 5:1. On the THIRD DAY, Esther stood in the inner court of the king's house. Many examples might be produced, from both the sacred and profane writers, in vindication of the propriety of the expression in the text. For farther satisfaction, the reader, if he please, may consult Whitby and Wakefield, and take the following from Lightfoot.

"I. The Jewish writers extend that memorable station of the unmoving sun, at Joshua's prayer, to six and thirty hours; for so Kimchi upon that place: 'According to more exact interpretation, the sun and moon stood still for six and thirty hours: for when the fight was on the eve of the Sabbath, Joshua feared lest the Israelites might break the Sabbath; therefore he spread abroad his hands, that the sun might stand still on the sixth day, according to the measure of the day of the Sabbath, and the moon according to the measure of the night of the Sabbath, and of the going out of the Sabbath, which amounts to six and thirty hours.'

"II. If you number the hours that pass from our Saviour's giving up the ghost upon the cross to his resurrection, you shall find almost the same number of hours; and yet that space is called by him three days and three nights, whereas two nights only came between, and one complete day. Nevertheless, while he speaks these words, he is not without the consent both of the Jewish schools and their computation. Weigh well that which is disputed in the tract Scabbath, concerning the separation of a woman for three days; where many things are discussed by the Gemarists, concerning the computation of this space of three days. Among other things these words occur: R. Ismael saith, Sometimes it contains four hwnwa onoth, sometimes five, sometimes six. But how much is the space of an hnwa onah? R. Jochanan saith, Either a day or a night. And so also the Jerusalem Talmud: 'R. Akiba fixed a DAY for an onah, and a NIGHT for an onah.' But the tradition is, that R. Eliazar ben Azariah said, A day and a night make an onah: and a PART of an onah is as the WHOLE. And a little after, R. Ismael computed a part of the onah for the whole." Thus, then, three days and three nights, according to this Jewish method of reckoning, included any part of the first day; the whole of the following night; the next day and its night; and any part of the succeeding or third day.

In the whale's belly] That a fish of the shark kind, and not a whale, is here meant, Bochart has abundantly proved, vol. iii. col. 742, &c., edit. Leyd. 1692. It is well known that the throat of a whale is capable of admitting little more than the arm of an ordinary man; but many of the shark species can swallow a man whole, and men have been found whole in the stomachs of several. Every natural history abounds with facts of this kind. Besides, the shark is a native of the Mediterranean Sea, in which Jonah was sailing when swallowed by what the Hebrew terms lwdg gd dag gadol, a great fish; but every body knows that whales are no produce of the Mediterranean Sea, thought some have been by accident found there, as in most other parts of the maritime world: but, let them be found where they may, there is none of them capable of swallowing a man. Instead of either whale or shark, some have translated lwdg gd dag gadol, Jon 1:17, by a fishing cove, or something of this nature; but this is merely to get rid of the miracle: for, according to some, the whole of Divine revelation is a forgery-or it is a system of metaphor or allegory, that has no miraculous interferences in it. But, independently of all this, the criticism is contemptible. Others say, that the great fish means a vessel so called, into which Jonah went, and into the hold of which he was thrown, where he continued three days and three nights. In short, it must be any thing but a real miracle, the existence of which the wise men, so called, of the present day, cannot admit. Perhaps these very men are not aware that they have scarcely any belief even in the existence of God himself!

MATTHEW 12:40. For as Jonas was--"a sign unto the Ninevites, so shall also the Son of man be to this generation" (Lu 11:30). For as Jonas was three days and three nights in the whale's belly-- (Jon 1:17).

so shall the Son of man be three days and three nights in the heart of the earth--This was the second public announcement of His resurrection three days after His death. (For the first, see Joh 2:19). Jonah's case was analogous to this, as being a signal judgment of God; reversed in three days; and followed by a glorious mission to the Gentiles. The expression "in the heart of the earth," suggested by the expression of Jonah with respect to the sea (Jon 2:3, in the Septuagint), means simply the grave, but this considered as the most emphatic expression of real and total entombment. The period during which He was to lie in the grave is here expressed in round numbers, according to the Jewish way of speaking, which was to regard any part of a day, however small, included within a period of days, as a full day. (See 1Sa 30:12,13; Es 4:16; 5:1; Mt 27:63,64, &c.).

From Albert Barns’ New Testament Commentary.

Matthew 12:40. For as Jonas was three days, etc. See Jon 1:17. This event took place in the Mediterranean Sea, somewhere between Joppa and Tarshish, when he was fleeing from Nineveh. It is said that the whale seldom passes into that sea, and that its throat is too small to admit a man. It is probable, therefore, that a fish of the shark kind is intended. Sharks have been known often to swallow a man entire. The fish in the book of Jonah is described merely as a great fish, without specifying the kind. It is well known that the Greek word translated whale, in the New Testament, does not of necessity mean a whale, but may denote a large fish of any kind.

Three days and three nights. It will be seen, in the account of the resurrection of Christ, that he was in the grave but two nights and a part of three days. See Mt 28:6. This computation is, however, strictly in accordance with the Jewish mode of reckoning. If it had not been, the Jews would have understood it, and would have charged our Saviour as being a false prophet; for it was well known to them that he had spoken this prophecy, Mt 27:63. Such a charge, however, was never made; and it is plain, therefore, that what was meant by the prediction was accomplished. It was a maxim, also, among the Jews, in computing time, that a part of a day was to be received as the whole. Many instances of this kind occur in both sacred and profane history. See 2Ch 10:5-12; Ge 42:17,18. Comp. Es 4:16 with Es 5:1.

In the heart of the earth. The Jews used the word heart to denote the interior of a thing, or to speak of being in a thing. It means, here, to be in the grave or sepulchre.

From Family Bible Notes

In the whale's belly; in which he was a type of Christ's burial. Three days and three nights; that is, parts of three days and nights. The burial of Christ took place on Friday. That was reckoned, according to Jewish custom, as one day. Saturday, through the whole of which Christ was in the tomb, called the heart of the earth, was another day; and the Christian Sabbath, on the morning of which he rose from the dead, was the third day; or according to their mode of speaking, three days and three nights.

From John Wesley’s notes on the Old and New Testaments.

Mat. 12:40 Mt 12:40 Three days and three nights-It was customary with the eastern nations to reckon any part of a natural day of twenty-four hours, for the whole day. Accordingly they used to say a thing was done after three or seven days, if it was done on the third or seventh day, from that which was last mentioned. Instances of this may be seen, 1Ki 20:29; and in many other places. And as the Hebrews had no word to express a natural day, they used night and day, or day and night for it. So that to say a thing happened after three days and three nights, was with them the very same, as to say, it happened after three days, or on the third day. See Es 4:16; 5:1; Ge 7:4,12; Ex 24:18; 34:28. Jon 2:1.

From Peoples New Testament Commentary

Matthew 12:40 Mt 12:40 As Jonah was three days and three nights in the belly of the great fish. See Jon 1:17. The great fish was probably not a whale (the Greek is [ketos], "sea monster"), but a white shark, which abounds in the Mediterranean, and is said to swallow a horse whole. The miracle was the preservation of the life of Jonah during his living burial. This was a type of the burial and resurrection of Christ.

So shall the Son of man be three days and three nights. Jesus says (Mt 16:21) that he will "be raised again the third day." Hence, in Jewish usage the third day must mean the same as three days and three nights. It was and is customary with the Orientals to make any part of the day stand for the whole twenty-four hours. Compare Mt 16:21; Mr 8:31; 2Ch 10:5,12; Es 4:16; Ge 7:4,12; Ex 24:18; 34:28. A traveler in the East writes: "At length the tenth morning arrived--the tenth morning because, though we performed nominally ten days quarantine, yet it was, really, only eight days. We landed at nine o'clock in the evening of the first day, and were liberated at six o'clock in the morning of the tenth day, but it was held to be ten days according to the custom of the East." Christ was buried Friday evening, lay in the grave Saturday, and rose Sunday, parts of three days, rose "on the third day," and was in the grave the space of time meant in eastern usage by three days and three nights.

In the heart of the earth. In the sepulcher.

The following was from the Forum at Eliyah’s
[This message has been edited by BarYah (edited 04-20-2003).]

This is actually a very difficult thing to figure out, because in getting in touch with the various astronomers and meteorologists that would have all the information about the "days and times" in the day of Mashiach, they cannot with perfect exactitude, tell us what went on during that week. And, throughout the believing world, there are various thoughts on the "three days and nights" meaning, as well as what Yeshua actually meant, when He said:

"An evil and adulterous generation seeketh after a sign; and there shall no sign be given to it, but the sign of the prophet Jonas" (Matthew 12: 39);

"A wicked and adulterous generation seeketh after a sign; and there shall no sign be given unto it, but the sign of the prophet Jonas. And he left them, and departed" (Matthew 16: 4);

and: Luke 11: 29: "This is an evil generation: they seek a sign; and there shall no sign be given it, but the sign of Jonas the prophet."

Here are some of the various difficulties:

These, I personally believe, have a valid point, for they say that the evidence looked for, for the whole world, and not only for the Hebrews, for only the Hebrews would really understand what these three days and three nights spoke of, was that at the preaching of Yeshua Mashiach, those who heard, believed, and repented, and there was a great army of believers that did so, after Yeshua's preaching and life. Nineveh was indeed a big city in those days of Jonah, but far more repented at Yeshua's preaching than did in the city of Nineveh.

Anyway, I leave these things in your hands. These are some of the arguments concerning the words of Yeshua in these above texts, and how many feel about the matter.

Personally, I believe that the week when Yeshua died, saw both the First Day of Unleavened Bread [a Sabbath when no work was to be done], and the weekly Sabbath, falling on the same weekly Sabbath, therefore that Sabbath was called a "High Day." This was considered a very special blessing, and worthy of note, and why not, for this would be the time when Yeshua, the world's Creator, would sleep in the grave, according to the commandment, thus ensuring for mankind that the Creator is our Redeemer, and the weekly Sabbath is that day which comes every seven, that causes us to celebrate that point.

Had this been practiced since the crucifixion, resurrection, and glorification of Yeshua Mashiach, there would have been no room for evolution, and the whole world by now, would understand this great truth about Who Yeshua is [the world's Creator (see Mark 2: 28)], Who came as a man, and also showed His immense love for His creation here, by taking our penalty, thus saving the world, and allowing that all who accept Him as their "Creator Who is their Saviour," and remain in a positive and agape-filled relationship with Him until the time of their deaths, will be found worthy of eternal life!

All such, have proven to the entire Universe, that they are filled with that Same Spirit Who filled Yeshua, and are just as safe as inhabitants of eternity [without anyone worrying about another rebellion occurring], as is the Saviour Himself, Who also overcame in the Land of the adversary, giving His faith to all of those who walk righteously in obedience to His commands and His Law of Agape.

Now, as to what happened that week, I believe that Yeshua Mashiach was taken on the Preparation of both the First Day of Unleavened Bread, or Passover, and that He was crucified and died with less than an hour to go before that Friday ending, and the weekly Sabbath [which was a High Day, so that the First Day of Unleavened Bread, and the Weekly Sabbath fell on that seventh-day] beginning. I believe that at the time of the entrance of Yeshua's body into the tomb of Joseph, which was possibly a half hour or less than, before the weekly Sabbath began, constituted one day [any part thereof], Yeshua rested the entire Sabbath Day according to the commandment for the weekly Sabbath, and the First Day of Unleavened Bread [see Leviticus 23, early part of chapter re: Passover],, and that just about a hour or a little more, before the sun came up on the first day [or we would say, Sunday today], He rose at the behest of His Father, gloriously coming forth, the last ten or eleven hours of the first day that He spent in the tomb, constituting the part of the third day that would be shown to be three days in Hebraic inclusive reckoning. When we see this with clarity, there is nothing to argue about.