But if we [really] are living and walking in the Light, as He [Himself] is in the Light, we have [true, unbroken] fellowship with one another, and the blood of Jesus Christ His Son cleanses (removes) us from all sin and guilt [keeps us cleansed from sin in all its forms and manifestations].

If we say we have no sin [refusing to admit that we are sinners], we delude and lead ourselves astray, and the Truth [which the Gospel presents] is not in us [does not dwell in our hearts].

If we [freely] admit that we have sinned and confess our sins, He is faithful and just (true to His own nature and promises) and will forgive our sins [dismiss our lawlessness] and [continuously] cleanse us from all unrighteousness [everything not in conformity to His will in purpose, thought, and action].