You know that he appeared in order to take away sins, and in him there is no sin.
5 And ye know that he was manifested, or, hath appeared. He shews by another argument how much sin and faith differ from one another; for it is the office of Christ to take away sins, and for this end was he sent by the Father; and it is by faith we partake of Christ’s virtue. Then he who believes in Christ is necessarily cleansed from his sins.
The apostle, having alleged the believer's obligation to purity from his hope of heaven, and of communion with Christ in glory at the day of his appearance, now proceeds to fill his own mouth and the believer's mind with multiplied arguments against sin, and all communion with the impure unfruitful works of darkness. And so he reasons and argues, I.
Commenting on 1 John 3:4-10
And ye know that he was manifested,.... This is a truth of the Gospel the saints were well instructed in and acquainted with; that Jesus Christ, the Word and Son of God, who is here meant, who was with the Father, and lay in his bosom from all eternity, was in the fulness of time made manifest in the flesh, or human nature, by assuming...