25 Let us dread then, brethren, lest God condemn us; who needs not examination or proofs, to condemn. Say not, In the night I committed fornication, or wrought sorcery, or did any other thing, and there was no man by. Out of your own conscience shall you be judged, your thoughts the meanwhile accusing or else excusing, in the day when God shall judge the secrets of men . The terrible countenance of the Judge will force you to speak the truth; or rather, even though thou speak not, it will convict you.
For you shall rise clothed with your own sins, or else with your righteous deeds. And this has the Judge Himself declared— for it is Christ who judges— for neither does the Father judge any man, but he has given all judgment unto the Son, not divesting Himself of His power, but judging through the Son; the Son therefore judges by the will of the Father; for the wills of the Father and of the Son are not different, but one and the same. What then says the Judge, as to whether you shall bear your works, or no? And before Him shall they gather all nations: (for in the presence of Christ every knee must bow, of things in heaven, and things in earth, and things under the earth:) and He shall separate them one from another, as the shepherd divides his sheep from the goats.
How does the shepherd make the separation? Does he examine out of a book which is a sheep and which a goat? Or does he distinguish by their evident marks? Does not the wool show the sheep, and the hairy and rough skin the goat? In like manner, if you have been just now cleansed from your sins, your deeds shall be henceforth as pure wool; and your robe shall remain unstained, and you shall ever say, I have put off my coat, how shall I put it on? By your vesture shall you be known for a sheep.
But if you be found hairy, like Esau, who was rough with hair, and wicked in mind, who for food lost his birthright and sold his privilege, you shall be one of those on the left hand. But God forbid that any here present should be cast out from grace, or for evil deeds be found among the ranks of the sinners on the left hand!
Source: Catechetical Lectures (New Advent)