"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."
Matthew 12:40 KJV
Unfortunately, Friday to Sunday isn't three days and three nights, so we are left to answer the question, why? Hard as it may be to believe, most believers do not know the answer to this because very few pastors have the answer. This might explain why they pass over this question and speak of other things at Easter, rather than investigating a seeming contradiction in scripture.
The reason many Christians can't answer this question has less to do with their knowledge of Christianity and much more to do with their lack of knowledge about Judaism. You see, most believers throughout the church age base their belief of a Friday crucifixion on the verses in the Gospels that state that Jesus was crucified the day before the Sabbath. This is why the Jews were in such a hurry to get Jesus off of the cross and into the tomb before sunset when the Sabbath would start, and everyone knows that the Sabbath is Saturday. So Jesus was crucified on Friday, right? Wrong.
You see, in Judaism although every Saturday is a Sabbath day, there are also other "High Sabbath" or "Holy Days" that are considered Sabbath days as well. These holidays on the Jewish calendar are much like our Christmas. We all know that Christmas is celebrated on December 25, and every year that occurs on a different day of the week because the calendar changes. It is the same for the High Sabbaths of Judaism. They occur on the same date on the Jewish calendar, but the day of the week it falls on is different every year.
One of these High Sabbaths is the Feast of Unleavened Bread, which occurs on the fifteenth day of the month of Nisan. It is the day after another Jewish holiday I'm sure you have heard of and that is Passover, which occurs on the fourteenth of Nisan. Now can you see where we are going with this? The days in Judaism begin at sundown, so although to us it was still Wednesday night, it was already the fourteenth or Passover. Jesus celebrated Passover with His disciples, and then went to the garden to pray where He was betrayed and taken into custody. The trial lasted until Thursday morning and by 9AM or so, Jesus was on the cross.
Since Friday was the Feast of Unleavened Bread, also a High Sabbath, the Jews were in a hurry to make sure Jesus was dead and buried by sundown Thursday, which was when the Sabbath would begin. Thursday, Friday, and Saturday day equals three days. Thursday, Friday, and Saturday night equals three nights. On Sunday morning Jesus rose from the grave and the prophecy was complete, just as He had foretold.
He is risen, He is risen indeed.