This is my own understanding - if you understand differently please do not take a personal offense. But when I had just begun to reckon sabbath by the moon, this was one of those questions that I had. As a christian and then as a messianic I was shown to interpret the phrase "in the heart of the earth" as "in the grave". Which makes perfect physical sense. However, I am being constantly moved in to the spiritual understanding of all matter. So, that being stated, please allow me to share how YHWH lead me to understand this phrase on a spiritual level.
The evil and adulterous nation asks for a sign that he IS the Messiah, due to their lack of faith, and Yahushua delivers this to them
Mat 12:38 Â¶ Then certain of the scribes and of the Pharisees answered, saying, Master, we would see a sign from thee.
Mat 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:
Mat 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.
So, the unbelieving were given their sign. They just had to wait for Yahushua to be gone from their physical sight for three days and three nights and then reappear in order to know that he IS Messiah - or did they
Later in the book of Matthew we see that Yahushua was meeting with his followers and stated the following:
Mat 26:1 Â¶ And it came to pass, when Jesus had finished all these sayings, he said unto his disciples,
Mat 26:2 Ye know that after two days is [the feast of] the passover, and the Son of man is betrayed to be crucified.
So, Yahushua knows his fate. He has proclaimed his fate out loud and it is the twelfth of the moon of Abib.
But then, something strange in the recording of Matthew - the Word FLASHES to what the chief priests and elders are doing - see the following:
Mat 26:3 Then assembled together the chief priests, and the scribes, and the elders of the people, unto the palace of the high priest, who was called Caiaphas,
Mat 26:4 And consulted that they might take Jesus by subtilty, and kill [him].
Mat 26:5 But they said, Not on the feast [day], lest there be an uproar among the people.
Okay, that was WIERD! Why did the story just flash like that? What else does Yahushua have to say about it?
Then, the answer came to me - NOTHING! He is the living word - he need not say anymore. He has chosen to place himself and his fate in the hearts of those who rule the land (aka - the earth) in that moment. We see the witness of it by the sudden change in setting that Matthew recorded.
So the count begins on the 12th day, then the 12th night, then the 13th day, then the 13th night, then the 14th day, then the 14th night and he rises before the morning on the fifteenth - why? I asked
And YHWH took me to this scripture:
Num 9:12 They shall leave none of it unto the morning, nor break any bone of it: according to all the ordinances of the passover they shall keep it.
If I am going to proclaim that Yahushua is the passover lamb, I must agree that none of him could remain until morning on the fifteenth. Therefore, I now understand that spiritually he was in the heart of the earth (where he placed himself through the spoken word) for three days and three nights on the 12th, 13th, and 14th.
Just a portion of what YHWH has walked me through. If anybody would like, I am very happy to share more on this topic. YHWH has given me harmony in my heart through His word on this matter so that I can rest in Him trusting that His word is true and remains true in all aspects. And I can also trust that Yahushua fulfilled the role of the passover lamb. (staked, his organs remained, roasted by fire =judged, no bones broken, gone before the fifteenth morning)