7 Let us even now become strangers; that God may “not be ashamed of us to be called our God.” For it is a shame to Him, when He is called the God of the wicked, and He also is ashamed of them; as He is glorified when He is [called the God] of the good and the kind, and of them that cultivate virtue. For if “we” decline to be called the masters of our wicked slaves, and give them up; and should any one come to us and say, 'such a one does innumerable bad things, he is your slave, is he not?' We immediately say, “by no means,” to get rid of the disgrace: for a slave has a close relation to his master, and the discredit passes from the one to the other. — But they were so illustrious, so full of confidence, that not only was He “not ashamed to be called” from them, but He even Himself says, “I am the God of Abraham, and the God of Isaac, and the God of Jacob.”
Let us also, my beloved, become “strangers”; that God may “not be ashamed of us”; that He may not be ashamed, and deliver us up to Hell. Such were they who said, “Lord, have we not prophesied in Your Name, and in Your Name have done many wonderful works!” But see what Christ says to them: “I know you not:” the very thing which masters would do, when wicked slaves run to them, wishing to be rid of the disgrace. “I know you not,” He says. How then dost Thou punish those whom You know not? I said, “I know not,” in a different sense: that is, “I deny you, and renounce you.” But God forbid that we should hear this fatal and terrible utterance. For if they who cast out demons and prophesied, were denied, because their life was not suitable thereto; how much more we!
Source: Homilies on the Epistle to the Hebrews (New Advent)