John Chrysostom

What then ought they to have done after this? Ought they not to have held their peace, and to have commended the saying? ought they not to have marvelled at His wisdom? ought they not to have stood amazed at His accordance with the Father? But none of these things do they, but as though they were contending for the law, they say, "How then did Moses command to give a writing of divorcement, and to put her away?" And yet they ought not now to have brought this forward, but rather He to them; but nevertheless He doth not take advantage …

Homily on the Gospel of Matthew 62 ↗

Theophylact of Ohrid

When the Pharisees saw that the Lord had confuted them, they were compelled to bring forward Moses as a lawgiver who contradicted Christ, and they asked, "Why did Moses then command to give a writing of divorcement, and to put her away?"

Commentary on Matthew ↗

Augustine of Hippo

For how great was that hardness! When not even the intervention of a bill of divorce, which gave room for just and prudent men to endeavour to dissuade, could move them to renew the conjugal affection. And with what wit do the Manichæans blame Moses, as severing wedlock by a bill of divorce, and commend Christ as, on the contrary, confirming its force? …

Catena Aurea by Aquinas ↗

Jerome

They said to him, 'So why did Moses command us to give a bill of divorce and dismiss?' They open the trap they had prepared. And certainly the Lord had not given his own opinion, but had remembered the old history and commandments of God.

Commentary on Matthew ↗

Thomas Aquinas

They say to him: why then did Moses command to give a bill of divorce, and to put away? Here their objection against the general law is presented: for they reveal what was in their mind. Why then did Moses command to give a bill of divorce and to put away? Moses did not command putting away, but indirectly wished to prohibit it, because Moses willed that a wife should not be put away unless a bill of divorce were given. …

Commentary on Matthew ↗