Thematic Bible: Why moses allowed divorce

They say unto him, Why did Moses then command to give a bill of divorce and to put her away? He said unto them, Moses, because of the hardness of your hearts, suffered you to put away your wives, but from the beginning it was not so.

And the Pharisees came to him and asked him, Is it lawful for a man to put away his wife? tempting him. And he answered and said unto them, What did Moses command you? And they said, Moses suffered to write a bill of divorce and to put her away. read more.
And Jesus answered and said unto them, For the hardness of your heart he wrote you this commandment. But at the beginning of the creation God made them male and female.