1 John 1:9

confess--with the lips, speaking from a contrite heart; involving also confession to our fellow men of offenses committed against them. he--God. faithful--to His own promises; "true" to His word. just--Not merely the mercy, but the justice or righteousness of God is set forth in the redemption of the penitent believer in Christ. God's promises of mercy, to which He is faithful, are in accordance with His justice. to--Greek, "in order that." His forgiving us our sins and cleansing us, &c., is in furtherance of the ends of His eternal faithfulness and justice. forgive--remitting the guilt. cleanse--purify from all filthiness, so that henceforth we more and more become free from the presence of sin through the Spirit of sanctification (compare Heb 9:14; and above, see on Jo1 1:7). unrighteousness--offensive to Him who "is just" or righteous; called "sin," Jo1 1:7, because "sin is the transgression of the law," and the law is the expression of God's righteousness, so that sin is unrighteousness.

— Jamieson-Fausset-Brown Commentary (public domain)