Deuteronomy 22:20-21 - "But if this charge is true, that the girl was not found a virgin, then they shall bring out the girl to the doorway of her father's house, and the men of her city shall stone her to death because she has committed an act of folly in Israel, by playing the harlot in her father's house; thus you shall purge the evil from among you."

This message from the Law of Moses is meant to ascribe two things on our hearts:
One, God takes our sin seriously.  We often forget that because we are so completely covered by the grace that is the Blood of Jesus Christ.  The truth is - God still feels the weight of our sin as heavy.  If nothing else, heavy on our souls.  Sin is a destroyer.

Two, God honors purity.  Read through the text and what you will find is a desire for the women (and men) of Israel to remain pure.  Purity is honored.  It still is today.

Joseph would have considered this verse when he found Mary to be with child.  This is why it is so valuable a statement: Joseph did not want to dishonor her, so he planned to divorce her in secret.

How much weight do you put on your sin?  On your purity?
How has God's love for us changed the face of punishment?
Looking at the burden sin presents, do you understand better the journey Christ went through on the cross for you?