Luke 12:9

But having confirmed them with good hope by so great promises, He again rouses them by more alarming threats, saying, But he that denieth me before men, shall be denied before the Angels of God. He rightly declares this threatening, in order that none should refuse to confess Him by reason of the punishment, which is to be denied by the Son of God, to be disowned by Wisdom, to fall away from life, to be deprived of light, and to lose every blessing; but all these things to suffer before God the Father who is in heaven, and the Angels of God.

Now they who deny are first indeed those who in time of persecution renounce the faith. Besides these, there are heretical teachers also, and their disciples.

He has also well introduced faith, stimulating us to its confession, and to faith itself He has placed virtue as a foundation. For as faith is the incentive to fortitude, so is fortitude the strong support of faith.

(ubi sup.) Both in condemnation a greater punishment is announced, and in blessing a greater reward; as if He said, Now you confess and deny, but I then, for a far greater recompense of good and evil awaits them in the world to come. There are other modes also of denying which St. Paul describes, saying, They profess that they know God, but in works they deny him. (Tit. 1:16.) And again, If any provide not for his own, and specially for those of his own house, he hath denied the faith, and is worse than an infidel. (1 Tim. 5:8.) Also, Flee from covetousness, which is idolatry. (Col. 3:5.) Since then there are so many modes of denial, it is plain that there are many likewise of confession, which whosoever has practised, shall hear that most blessed voice with which Christ greets all who have confessed Him. But mark the precaution of the words. For in the Greek he says, Whosoever shall confess in Me, showing that not by his own strength, but by the aid of grace from above, a man confesses Christ. But of him who denies, He said not "in Me," but me. For though being destitute of grace he denies, he is nevertheless condemned, because the destitution is owing to him who is forsaken, or he is forsaken for his own fault.