1 John 1:5-7

Verse 5

This then is the message - This is the grand principle on which all depends, which we have heard of απ' αυτου, From him; for neither Moses nor the prophets ever gave that full instruction concerning God and communion with him which Jesus Christ has given, for the only-begotten Son, who was in the bosom of the Father, has alone declared the fullness of the truth, and the extent of the blessings, which believers on him are to receive. See Joh 1:18.

God is light - The source of wisdom, knowledge, holiness, and happiness; and in him is no darkness at all - no ignorance, no imperfection, no sinfulness, no misery. And from him wisdom, knowledge, holiness, and happiness are received by every believing soul. This is the grand message of the Gospel, the great principle on which the happiness of man depends. Light implies every essential excellence, especially wisdom, holiness, and happiness. Darkness implies all imperfection, and principally ignorance, sinfulness, and misery. Light is the purest, the most subtile, the most useful, and the most diffusive of all God's creatures; it is, therefore, a very proper emblem of the purity, perfection, and goodness of the Divine nature. God is to human soul, what the light is to the world; without the latter all would be dismal and uncomfortable, and terror and death would universally prevail: and without an indwelling God what is religion? Without his all-penetrating and diffusive light, what is the soul of man? Religion would be an empty science, a dead letter, a system unauthoritated and uninfluencing, and the soul a trackless wilderness, a howling waste, full of evil, of terror and dismay, and ever racked with realizing anticipations of future, successive, permanent, substantial, and endless misery. No wonder the apostle lays this down as a first and grand principle, stating it to be the essential message which he had received from Christ to deliver to the world.
Verse 6

If we say that we have fellowship - Having fellowship, κοινωνια, communion, with God, necessarily implies a partaking of the Divine nature. Now if a man profess to have such communion, and walk in darkness - live an irreligious and sinful life, he lies, in the profession which he makes, and does not the truth - does not walk according to the directions of the Gospel, on the grace of which he holds his relation to God, and his communion with him.

The Gnostics, against whose errors it is supposed this epistle was written, were great pretenders to knowledge, to the highest degrees of the Divine illumination, and the nearest communion with the fountain of holiness, while their manners were excessively corrupt.
Verse 7

But if we walk in the light - If, having received the principle of holiness from him, we live a holy and righteous life, deriving continual light, power, and life from him, then we have fellowship one with another; that is, we have communion with God, and God condescends to hold communion with us. This appears to be the intention of the apostle; and so he was understood by some versions and MSS., which, instead of μετ' αλληλων, with each other, have μετ' αυτον, with him. Those who are deeply experienced in Divine things converse with God, and God with them. What John says is no figure; God and a holy heart are in continual correspondence.

The blood of Jesus Christ - The meritorious efficacy of his passion and death has purged our consciences from dead works, and cleanseth us, καθαριζει ἡμας, continues to cleanse us, i.e., to keep clean what it has made clean, (for it requires the same merit and energy to preserve holiness in the soul of man, as to produce it), or, as several MSS. and some versions read, καθαριει and καθαρισει, will cleanse; speaking of those who are already justified, and are expecting full redemption in his blood.

And being cleansed from all sin is what every believer should look for, what he has a right to expect, and what he must have in this life, in order to be prepared to meet his God. Christ is not a partial Savior, he saves to the uttermost, and he cleanses from All sin.
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