- Some sticklers notice that Friday afternoon to Sunday morning is only a day and a half, not three days. Greek writings, especially those written by Jews, used three phrases interchangeably: "three days and three nights" "after three days" and "on the third day." All mean something like "the day after tomorrow." I have seen the phrases used interchangeably in the Gospels, in Josephus, and in Esther 4:16-5:1.
- Jesus raised Lazarus from the dead after four days (John 11:17); mentioning the four days shows how certain it was that Lazarus was dead. In the same way, Jesus' three days in the tomb shows the certainty of his death. (Later rabbinic documents show that some Jews believed that it was possible to raise someone from the dead, but only in the first three days; that might be interesting, but we have no idea if Jews at the time of Jesus believed that).
- Many Christians throughout history have believed that Jesus went to hell during the three days, either experiencing full punishment for our sins, or releasing OT faithful from imprisonment, or preaching to the damned (the so-called "harrowing of hell"). However, the four gospels say nothing about where Jesus was. Some interpret 1 Pet 3:18-20 to mean that Jesus was in hell; but most NT scholars don't think that's what Peter meant.
The picture: "Descent to Hell" by Duccio di Buoninsegna, 1308. Jesus is shown trampling Satan and helping Adam and Eve up.