After the crucifixion Jesus was in the tumb for three days. In western terms we think of three days and three nights. In ancient Israel (and even Israel today) a day begins at 6:00pm in the evening. An example of this is Genesis 1:5

God called the light Day, and the darkness He called Night. So the evening and the morning were the first day.

Obviously this puts the crucifixion on Thursday afternoon. From the Jewish standpoint Friday night actually occurs on what we call Thursday evening.

This is not my inquiry though.

Jesus made mention of being buried for three days using Jonah as an example. The question I've wondered about is:

Why three days? Why (roughly) 72 hours? Why not 1 day (24 hours)?