Ambrose of Milan, on Ps 54:12

“And injustice. And usury and deceit have not departed from its streets.”

“So one who does the will of God is his friend and is honored with this name. He who is of one mind with him, he too is his friend. For there is unity of mind in friends, and no one is more hateful than the person who injures friendship. Hence in the traitor the Lord found this the worst point on which to condemn his treachery, namely, that Judas gave no sign of gratitude and had mingled the poison of malice at the table of friendship. So he says, "It was you, a man of like mind, my guide and my acquaintance, who ever did take pleasant meals with me." That is: it could not be endured, for you did fall on him who granted grace to you. "For if my enemy had reproached me I could have borne it, and I would have hid myself from him who hated me." An enemy can be avoided; a friend cannot, if he desires to lay a plot. Let us guard against him to whom we do not entrust our plans; we cannot guard against him to whom we have already entrusted them. And so to demonstrate all the hatefulness of the sin he did not say, You, my servant, my apostle; but you, a man of like mind with me; that is, you are not my betrayer but your own, for you did betray a man of like mind with yourself.”

Imported from an open dataset — not yet checked against the printed edition.