If we confess our sins, he is faithful and just to forgive us our sins, and to cleanse us from all unrighteousness.
Confess - with the lips, from a contrite heart; involving confession to our fellow-men of offences against them.
He - God.
Faithful - to His own promises: 'true' to His word.
Just. Not merely the mercy, but the justice of God is set forth in the redemption of the penitent believer in Christ. God's promises of mercy, to which lie is faithful, harmonize with His justice (Romans 3:25-26).
To, х hina (G2443)] - 'in order that.' His forgiving us our sins and cleansing us from, etc., further the ends of His eternal faithfulness and justice.
Forgive - remitting the guilt.
Cleanse - purify from filthiness. Henceforth we more and more become free from the presence of sin through the Spirit of sanctification (cf. Hebrews 9:14; above, note, 1 John 1:7).
Unrighteousness - offensive to Him who 'is just.' Called "sin," 1 John 1:7, because "sin is the transgression of the law," and the law is the expression of God's righteousness; so sin is unrighteousness.