He answered and said to them, “What did Moses command you?”
The Lord answers their question with a question, bringing them back to the foundations of Holy Scripture. He does not accept human custom as the final standard, but requires them to think about God’s revealed will. The words “What did Moses command you?” also reveal the condition of their heart: they knew well the letter of the law, but often lost its spirit. Christ compels them to confess the basis on which they themselves were relying, so that afterward He may show that the permission of divorce found in the law of Moses was not the perfect expression of God’s original will, but was given because of the hardness of people’s hearts. This teaches that in divine matters one should not be guided by social custom or personal desire, but should seek the true meaning of the word of God.