Mark 10:5
It was because your hearts were hard that Moses wrote you this law, Jesus replied — the hardness-of-heart explanation for the Mosaic divorce permission is Jesus' most important move in the discussion. Moses did not ordain divorce as God's design; he regulated a practice that was happening due to human sinfulness, providing legal protection within a fallen situation. The divorce certificate was damage control, not divine ideal. The existence of the Mosaic permission reveals the condition of the people's hearts, not the will of God for marriage.