If we confess our sins, he is faithful and righteous to forgive us the sins, and to cleanse us from all unrighteousness.
he is faithful and just to forgive us our sins: God will forgive us. Why? Because He is "faithful and just" to do so. God is true and faithful to His nature and His promises. He always acts in consistency with His nature and can never be out of character with Himself. God promises to forgive, and He will surely keep His word (Hebrews 10:23; Hebrews 11:11; 1 Thessalonians 5:24; 1 Corinthians 1:9; 2 Timothy 2:13). He is also "just" or righteous. God always does that which is right and just. He is just in forgiving us of our sins because of the blood of Jesus Christ that satisfied the justice of God. To "forgive" means, literally, to send away, dismiss, according to Vincent (322). When God forgives, He sends our sins so far away they are never remembered again (Hebrews 8:12). He dismisses them from His mind and removes their guilt from our lives. John says that God forgives "our sins." In verse 8, he writes of "sin" or sinfulness in our lives; in this verse, he focuses on the specific sins we confess.