The problem with using this as proof is that the "days ago" is how many days ago he fell sick, and "three days and three nights" is how long ago he didn't eat or drink. The two things are not neccesarily related. You're drawing the conclusion that the two events (not eating, and being sick) must match up. You're assuming that he didn't eat anything or drink on the first day or night that he was sick.
But let's get to the meat of the matter:
Mat 12:40 for just as JONAH WAS THREE DAYS AND THREE NIGHTS IN THE BELLY OF THE SEA MONSTER, so will the Son of Man be three days and three nights in the heart of the earth.
Compare with:
Jon 1:17 And the LORD appointed a great fish to swallow Jonah, and Jonah was in the stomach of the fish three days and three nights.
Scripturally, Jesus HAD to be in the grave the same amount of time that Jonah was in the fish or else he was not the messiah.
So let's look at it the opposite way...how long was Jonah IN the fish? As far as I can tell, it has always been understood to be literally three days and three nights. Not parts of days and nights to equal 3, but a literal three days and three nights.
However, you are espousing the position that no, Jonah was NOT actually in the fish for three days and three nights, but was in the fish for something less than three days and three nights and that this too, is an idiom. In fact, your position is that this idiom is applied TWICE, once in the new testament and once in the old testament, to designate a time period that IS KNOWN.
Let me repeat this is bold: Your position is that this idiom is applied TWICE, once in the new testament and once in the old testament, to designate a time period that IS KNOWN.
In other words, instead of just putting down the actual number of days and nights that Jonah was in the fish AND Jesus was in the earth, God had to generalize and confuse the issue by inspiring a non-specific idiom to be used. Is that credible?
Now from some preliminary research I've done, the understanding of the story of Jonah is that it's a literal three days and three nights that Jonah was in the fish and that this has been the understanding for milleniums. I've emailed the question to a rabbi to ask if what the traditional jewish understanding was of the time frame that Jonah spent in the fish. I'll share that info when it comes.
Why 72 hours? Because Jesus Christ affirms that a day is 12 hours:
Joh 11:9 Jesus answered, "Are there not twelve hours in the day? If anyone walks in the day, he does not stumble, because he sees the light of this world.
Since a day is 12 hours, then a night is also 12 hours.
Let me illustrate this another way.
Mat 12:38 Then some of the scribes and Pharisees said to Him, "Teacher, we want to see a sign from You."
Mat 12:39 But He answered and said to them, "An evil and adulterous generation craves for a sign; and yet no sign will be given to it but the sign of Jonah the prophet;
Mat 12:40 for just as JONAH WAS THREE DAYS AND THREE NIGHTS IN THE BELLY OF THE SEA MONSTER, so will the Son of Man be three days and three nights in the heart of the earth.
You're saying that Jesus Christ was basing his messiahship on an idiom who's exact time length was unknown AT THE TIME. Or, you're saying that the Pharisee's understood that Jonah was NOT in the fish three days and three nights, but instead was only in there 2 nights and 1 day. How they knew this without Christ being dead in the grave is a mystery indeed.
Mat 12:40 for just as JONAH WAS THREE DAYS AND THREE NIGHTS IN THE BELLY OF THE SEA MONSTER, so will the Son of Man be three days and three nights in the heart of the earth.
Compare with:
Jon 1:17 And the LORD appointed a great fish to swallow Jonah, and Jonah was in the stomach of the fish three days and three nights.
Scripturally, Jesus HAD to be in the grave the same amount of time that Jonah was in the fish or else he was not the messiah.
Perhaps, but Mat 12:40 doesn't say Jesus. It says "son of man" (idiom for a human being). And it doesn't say grave, it says "heart of the earth". Resurrection timing theories aside, the traditional assumption that he spoke of himself in the grave may be correct, but considering church track record on interpretation, I'd rather mark this one as "subject to further clarification." It's not like there is another NT passage that describes Jesus by name as spending three days and three mights in the grave, so I am leery of making that leap. The closest NT reference to three days and three nights (besides Jonah) is in Revelation 11, where the two prophets lie dead in the street for three days and a half. Then they rise and are beheld by their enemies.
So unless, for example, the earth is alive with a literal beating heart, the phrase "heart of the earth" is metaphorical. Could be a grave, but a city that is spiritually equated to Sodom and Egypt is a city with a corrupt heart, and considering that...
Matthew 6:21 For where your treasure is, there will your heart be also.
... the heart of a wicked earth would be as Sodom and Egypt. Or say, Babylon.
Besides, there are two prophets addressed as ben adam: Ezekiel, and also Daniel. I am not claiming that the prophets of Revelation 11 are literal and are Ezekiel and Daniel (e.g. the prophets could represent the two houses/sticks of Israel, and/or the Law and the Prophets, and/or the Torah rollers - etz chaim), only that a closer inspection of Mat 12:40 does lead in an alternate direction. If the followers of Jesus insist that he (Jesus) was the sign of the prophet Jonah, then they inadvertantly identify themselves with an evil and adulterous generation.
Matthew 12:39 But he answered and said unto them, 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 12:40 For as Jonas was three days and three nights in the whale's belly; so shall the Son of man be three days and three nights in the heart of the earth.
Yet over at Revelation 11, who observed the dead prophets in the street and sent presents to each other, happy those prophets had finally stopped harassing them?
Revelation 11:8-12
8 And their dead bodies shall lie in the street of the great city, which spiritually is called Sodom and Egypt, where also our Lord was crucified.
9 And they of the people and kindreds and tongues and nations shall see their dead bodies three days and an half, and shall not suffer their dead bodies to be put in graves.
10 And they that dwell upon the earth shall rejoice over them, and make merry, and shall send gifts one to another; because these two prophets tormented them that dwelt on the earth.
11 And after three days and an half the Spirit of life from God entered into them, and they stood upon their feet; and great fear fell upon them which saw them.
12 And they heard a great voice from heaven saying unto them, Come up hither. And they ascended up to heaven in a cloud; and their enemies beheld them.
2588 kardia {kar-dee'-ah}
prolonged from a primary kar (Latin, cor, "heart"); TDNT - 3:605,415; n f
AV - heart 159, broken hearted + 4937 1; 160
1) the heart
1a) that organ in the animal body which is the centre of the
circulation of the blood, and hence was regarded as the seat
of physical life
1b) denotes the centre of all physical and spiritual life
2a) the vigour and sense of physical life
2b) the centre and seat of spiritual life
2b1) the soul or mind, as it is the fountain and seat of the
thoughts, passions, desires, appetites, affections,
purposes, endeavours
2b2) of the understanding, the faculty and seat of the
intelligence
2b3) of the will and character
2b4) of the soul so far as it is affected and stirred in a
bad way or good, or of the soul as the seat of the
sensibilities, affections, emotions, desires,
appetites, passions
1c) of the middle or central or inmost part of anything, even
though inanimate
I suspect this study will go over as "well" as it always does. :-/