From this view of the divine nature, the Apostle now deduces what is required as the condition of standing in fellowship with God; the signs by which this fellowship will manifest itself in the life; and on the other hand, by what signs it is to be known that no such fellowship exists. "If we say that we have fellowship with him and walk in darkness, we lie, and do not the truth: but if we walk in the light, as he is in the light, we have fellowship one with another, and the blood of Jesus Christ his Son cleanseth us from all sin."

The thought here lying at the basis is this: that since all spiritual fellowship presupposes an affinity of nature, and this inward fellowship of nature must also have an outward manifestation in the life; so no fellowship with God can exist without a life conformed to God. Since then God is light, fellowship with him must manifest itself through a life which is full of light; fellowship with the God whose nature is holiness, through a holy course of life. John does not here mean a quality of the life-walk required for the first attainment of fellowship with God; but assuming this divine fellowship of life, received through faith in the Redeemer, as already existing, his object is to point out the tests, whether the claim to such a fellowship be true or false, -- whether the Christianity which is professed be a true, or merely a seeming and pretended one. This thought is expressed, in John's peculiar manner, both in the negative and affirmative form. Ile first says, in opposition to that mere seeming Christianity, that he who leads an ungodly life, and yet claims to be in fellowship with God, thereby makes himself guilty of a lie. Full of significance is the expression, "We do not the truth"; an expression belonging to the depth of conception peculiar to John. With him truth is not limited in its application to speech merely; it embraces the entire life. The entire life has its root either in falsehood or in truth. Truthfulness in speech is but one index of that truth which embraces, fills, vitalizes the whole inner and outer life. Hence, of one who makes claim to something which is contradicted by his course of life it is said, that his whole life is alien from the truth, that he does not practice the truth, that his life is chargeable with falsehood. Speech appears also as an action; -- "We do not the truth."

In contrast with this, John designates "Walking in the Light," in holiness, as a mark of fellowship with God who is in the light, who reveals himself in holiness. "If we walk in the light as He is in the light, then have we fellowship one with another." He does not speak here directly of fellowship with God, but of the fellowship of believers with one another; but in this is necessarily presupposed fellowship with God through Christ, as that from which the fellowship of believers with one another first proceeds. John thus distinguishes between those who belong, as true members, to the fellowship of Christians (in other words to the church, a designation never used by John) and those who belong to it only in appearance and not in truth, those whose pretensions are contradicted by their ungodly life. Fellowship with God, as effected through Christ, and the fellowship of believers with each other, is here one and the same thing.

If now the life of believers while here on earth were already a perfect fellowship with God, if their course of life were a walking in the light free from darkness of every kind, and unstained by any farther act of sin, then John would have had no occasion to add anything more. But he was well aware that even in believers, although their life is in its determining tendency a walking in the light, yet the dark, the sinful, still mingle with it their disturbing influence; the former stand-point of darkness and sin, from which redemption has set them free, still remains in its effects. Hence, this "walking in the light" must be developed in a continuous conflict with the former darkness; from the light already received, the whole life must be gradually transformed into light. And hence, in reference to that sinfulness which still cleaves to the believer and opposes itself to the light, he says, that where that walking in the light exists as the determining tendency, the mark of fellowship with God, there the blood of Jesus Christ will make known its purifying efficacy, its power to cleanse from all still inhering sin.

In the purification through the blood of Christ, we are obviously not to understand the blood of. Christ literally, nor an outward literal purification by it, anymore than the sprinkling of the conscience with the blood of Christ, spoken of in the Epistle to the Hebrews, is to be so understood. Only a spiritual cleansing can here be meant, and consequently only a spiritual means of cleansing. It is necessary to refer back the sensible imagery to the thought imaged therein. It is the language of the Holy Scriptures, the language of life; according to which one characteristic of the whole is put for the whole itself; and especially is that which appears as the crowning point put for the whole with all its characteristics, so that the single characteristic must be conceived of in that connection, in union with the sum of all the others, in order to be rightly understood. The blood of Christ, then, must be conceived of in its full significance, as it was present to the view of the Apostle, viz. as both a Doing and a Suffering; it being on the one hand a suffering for the guilt of humanity, and presenting on the other, in the perfect holiness of the life of Christ, an offset to the sin of humanity, a thought which we shall hereafter find still further developed in other expressions of John. Since now this suffering of Christ, once for all, possesses this redeeming and purifying significance, it continues to perform its work in all those who through faith enter into fellowship with Christ, till all in them that is sinful shall be cleansed away, and all be transformed into light. In this idea of purification two distinct things are included; namely, first, that the sin which yet remains shall no longer form a hindrance to fellowship with God, it shall be as if already done away, -- the forgiveness of sins; and secondly, that the still operating sinful element shall actually be more and more cleansed away, -- the progressive purification of the whole life. All this is an ever progressing appropriation of the once perfected redemption.

So in what John here says, we find two different things expressed. It is assumed that there is sin yet cleaving to those who are walking in light; though in fellowship with Christ, they are still in constant need of redemption through him, in constant need of him as the Redeemer; that we who are walking in the light with Christ in us, have also still need of Christ for us. To those who, while walking uprightly in the light, are yet daily conscious to themselves of the still remaining influence of sin; who cannot but perceive in their own life much whereby the light which is in them is darkened, and who might be disquieted in conscience, when told that only those who walk in the light can stand in fellowship with God who is Light; to them is offered the consoling assurance of entire purification from their yet inhering sin. But the Apostle guards also against the self-deception of those, who trust to purification through the blood of Christ without a course of life corresponding to such an expectation, without the outward signs of an inward divine fellowship of life through Christ. Only those are to expect this purification, who, through the determining tendency of their lives, make it manifest that they stand in that divine fellowship and are sanctified thereby. Thus the close connection between the Christ in us and the Christ for us, is here indicated.