1:5-10 A message from the Lord Jesus, the Word of life, the eternal Word, we should all gladly receive. The great God should be represented to this dark world, as pure and perfect light. As this is the nature of God, his doctrines and precepts must be such. And as his perfect happiness cannot be separated from his perfect holiness, so our happiness will be in proportion to our being made holy. To walk in darkness, is to live and act against religion. God holds no heavenly fellowship or intercourse with unholy souls. There is no truth in their profession; their practice shows its folly and falsehood. The eternal Life, the eternal Son, put on flesh and blood, and died to wash us from our sins in his own blood, and procures for us the sacred influences by which sin is to be subdued more and more, till it is quite done away. While the necessity of a holy walk is insisted upon, as the effect and evidence of the knowledge of God in Christ Jesus, the opposite error of self-righteous pride is guarded against with equal care. All who walk near to God, in holiness and righteousness, are sensible that their best days and duties are mixed with sin. God has given testimony to the sinfulness of the world, by providing a sufficient, effectual Sacrifice for sin, needed in all ages; and the sinfulness of believers themselves is shown, by requiring them continually to confess their sins, and to apply by faith to the blood of that Sacrifice. Let us plead guilty before God, be humble, and willing to know the worst of our case. Let us honestly confess all our sins in their full extent, relying wholly on his mercy and truth through the righteousness of Christ, for a free and full forgiveness, and our deliverance from the power and practice of sin.

7. Compare Eph 5:8, 11-14. "We walk"; "God is (essentially in His very nature as 'the light,' 1Jo 1:5) in the light." Walking in the light, the element in which God Himself is, constitutes the test of fellowship with Him. Christ, like us, walked in the light (1Jo 2:6). Alford notices, Walking in the light as He is in the light, is no mere imitation of God, but an identity in the essential element of our daily walk with the essential element of God's eternal being.

we have fellowship one with another—and of course with God (to be understood from 1Jo 1:6). Without having fellowship with God there can be no true and Christian fellowship one with another (compare 1Jo 1:3).

and—as the result of "walking in the light, as He is in the light."

the blood of Jesus … cleanseth us from all sin—daily contracted through the sinful weakness of the flesh, and the power of Satan and the world. He is speaking not of justification through His blood once for all, but of the present sanctification ("cleanseth" is present tense) which the believer, walking in the light and having fellowship with God and the saints, enjoys as His privilege. Compare Joh 13:10, Greek, "He that has been bathed, needeth not save to wash his feet, but is clean every whit." Compare 1Jo 1:9, "cleanse us from all unrighteousness," a further step besides "forgiving us our sins." Christ's blood is the cleansing mean, whereby gradually, being already justified and in fellowship with God, we become clean from all sin which would mar our fellowship with God. Faith applies the cleansing, purifying blood. Some oldest manuscripts omit "Christ"; others retain it.