Mark 10:9-12 are the words of Jesus. I'm not sure what the question is about this verse. Jesus is very clear, if you get a divorce, you may not get married again. Yes, Christians get divorced and remarried. However, that does not change what God has said. All that means is that we are not perfect and we do things we should not do (that's called sin). And because God is just, we can't just get away with disobeying Him. There is a penalty to be paid. But getting back to the Mark 10:9-12...

This is what Mark 10:9-12 says (NIV):

"Therefore what God has joined together, let no man separate.

When they were in the house again, the disciples asked Jesus about this. He answered, 'Anyone who divorces his wife and marries another woman commits adultery against her. And if she divorces her husband and marries another man, she commits adultery.'"

Why is God so strict about divorce? He gives the answer in just three words in Malachi 2:16, "I hate divorce," says the Lord God of Israel..."

The only exception, which is if your spouse dies, is given to us in Romans 7:1-3 (NIV)

"Do you not know brothers--for I am speaking to men who know the law--that the law has authority over a man only as long as he lives? For example, by law a married woman is bound to her husband as long as he is alive, but if her husband dies she is released from the law of marriage. So then, if she marries another man while her husband is still alive, she is called an adulteress. But if her husband dies, she is released from the law and is not an adulteress, even though she marries another man."