In confessing sin the Christian is not telling God something he doesn't already know, but is taking ownership of his sin, turning from it, and seeking pardon and peace in the face of Christ. Confession exalts God, his law, and his gospel.
Every man ought to make private confession of his sins to God. We cannot discover to God anything that was previously concealed from his omniscient eye; but by confessing our sins we give glory to God, as well as take shame to ourselves. Hence Joshua said unto Achan: "My son, give, I pray thee, give glory to the Lord God of Israel, and make confession unto him."–Josh vii 19. To cover our sins is to dishonour God, as if he either did not see, or could not punish them; whereas, to confess our sins is to honour God's holy law, which we have violated–to honour his omniscience, which beheld all our transgressions–to honour his justice, which might have taken vengeance upon them–and to honour his patience and longsuffering, which have forborne to execute the merited punishment.
- Rober Shaw, The Reformed Faith