Therefore pray not for this people, neither lift up cry nor prayer for them, neither make intercession to me: for I will not hear you.
Read Chapter 7
Ambrose of Milan
AD 397
Rightly, then, is it said, “Who shall entreat for him?” It implies that it must be such a one as Moses to offer himself for those who sin. Or such as Jeremiah, who, though the Lord said to him, “Pray not for this people,” yet prayed and obtained their forgiveness. For at the intercession of the prophet and the entreaty of so great a seer, the Lord was moved. And Jerusalem, which had meanwhile repented for its sins, had said, “O Almighty Lord God of Israel, the soul in anguish and the troubled spirit cries to you. Hear, O Lord, and have mercy.” - "Concerning Repentance 1.9.43"
Praise, offered to appease my wrath. (Haydock)
This admirably shows the force of the saints' intercession, which God does not reject, but rather encourages by such declarations. Abraham and Moses did not leave off praying for the guilty, (Genesis xviii. 23., and Exodus xxxii. 10.) and the Lord complains that there was none to withhold him, Isaias lxiv. 7., and Ezechiel xxii. 30. (Calmet)
He did the same thing in explaining himself to Noah about the flood that he did to Ezekiel when while living in Babylon he caused him to see the people’s evil deeds in Jerusalem. And when he told Jeremiah not to pray, there too he explained himself adding, “Do you not see what they do?” And he does the same thing everywhere as he does here [in Matthew]. For what does he say? “The people of Nineveh shall rise up and shall condemn this generation, because they repented at the preaching of Jonah, and, behold, a greater one than Jonah is here.” - "Homilies on the Gospel of Matthew 43.3"
Just as God knows how to heal, so does he furthermore know how to smite. He knows how to make peace but likewise permits evils. He prefers repentance but moreover commands Jeremiah not to pray for the reversal of ills on behalf of the sinful people. He says, “If they will fast, I still will not listen to their plea.” And again: “Do not pray to me on behalf of the people, and do not request on their behalf in prayer and supplication, since I will not listen to them in the time when they shall have invoked me, in the time of their affliction.” And further he, the same One who prefers mercy above sacrifice, says, “And do not pray to me on behalf of this people, and do not request that they may obtain mercy, and do not approach me on their behalf, since I will not listen to them in the time wherein they shall have invoked me, in the time of their affliction.” - "On Purity 2"
