Question: is it lawful for a man to divorce his wife for any reason?
Jesus: quotes scriptures from Genesis: man shall leave his father and mother and the two become one flesh. Man leaves his parents and is joined to his wife. What God has joined together let no one separate.
Question: why did Moses allow certificates of divorce to put a wife away?
Answer: because of your hard hearts. But from the beginning it was not so.
Jesus final word on it: don't divorce your wife - except for the reason of sexual immorality - if you divorce your wife and marry another you are committing adultery. And the one who marries a divorced wife also commits adultery.
Jesus lays out the laws for marriage pretty clearly. Divorce should not be an option. He wants people to work on their marriages... To be one flesh. To leave father and mother behind.
What God has joined together let no man separate.