Whedon's Commentary on the Bible - Matthew 12:40
40. Three days His resurrection, connected with the diurnal revolution, would be an astronomical sign. Our Saviour was not in the tomb three days and three entire nights, according to our modes of calculation. He expired on Friday afternoon and rose on Sunday morning. He was therefore entombed but the nights of Friday and Saturday. But the Jews reckoned the entire twenty-four hours in an unbroken piece, as a night-and-day. They counted the odd fragment of a day, in computation, as an... read more
Wesley's Explanatory Notes - 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.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, 1 Kings 20:29;... read more