In verse 21 John goes on to conclude “Little children, guard yourselves from idols.” The word “guard” means to garrison ourselves against attacks from without, like the assaults of the heresies. “Idols” refers to the heretical substitutes, brought in by the Gnostics and Cerinthians, for the true God, as revealed in this Epistle and in John’s Gospel and referred to in the preceding verse. Idols here also refer to anything that replaces the real God. We as genuine children of the genuine God should be on the alert to guard ourselves from these heretical substitutes and all vain replacements of our genuine and real God, with whom we are organically one and who is eternal life to us. This is the aged apostle’s word of warning to all his little children as a conclusion of his Epistle.
According to John’s understanding, an idol is anything that replaces, is a substitute for, the subjective God, the God whom we have experienced and whom we are still experiencing. Through this enlightenment, we are able to understand 5:18-21 in a very experiential way.
Before we were saved, we were outside of God. God was true in Himself, but we could not say in our experience that He was true to us. But after we believed in the Lord Jesus, we entered into God. Therefore, 5:20 says not only that we know the true One, but also that we are in the true One. We have seen that to be in the true One means that we are in His Son Jesus Christ. Because we are in God, He now experientially becomes true to us. Likewise, because we are in Jesus Christ, He becomes experientially true to us. Due to our experience of God and Christ by being in God and in Christ, we can say that this is the true God and eternal life.
The word “this” in 5:20 implies that God, Jesus Christ, and eternal life are one. In doctrine, there may be a distinction between God, Christ, and eternal life, but in our experience they are one. When we are in God and in Jesus Christ and when we experience eternal life, we find that all these are one. Therefore, John concludes verse 20 by saying, “This is the true God and eternal life.” This sentence is not merely the conclusion of verse 20; it is actually the conclusion of the entire book. What this Epistle reveals is the true God and eternal life.
John’s last word, in 5:21, is the charge to guard ourselves from idols. Anything that is a substitute or replacement for the true God and eternal life is an idol. We need to live, walk, and have our being in this God and in this life. If we do not live in the true God and eternal life, then we shall have a substitute for the true God, and this substitute will be an idol.
The center of the revelation in this Epistle is the divine fellowship of the divine life, the fellowship between the children of God and their Father God, who is not only the source of the divine life, but also light and love as the source of the enjoyment of the divine life (1:1-7). To enjoy the divine life we need to abide in its fellowship according to the divine anointing (2:12-28; 3:24), based upon the divine birth with the divine seed for its development (2:29—3:10). This divine birth was carried out by three means: the terminating water, the redeeming blood, and the germinating Spirit (5:1-13). By these we have been born of God to be His children, possessing His divine life and partaking of His divine nature (2:29—3:1). He is now indwelling us through His Spirit (3:24; 4:4, 13) to be our life and life supply that we may grow with His divine element unto His likeness at His manifestation (3:1-2).
To abide in the divine fellowship of the divine life, that is, to abide in the Lord (2:6; 3:6), is to enjoy all His divine riches. By such abiding, we walk in the divine light (1:5-7) and practice the truth, righteousness, love, the will of God, and His commandments (1:6; 2:29, 5; 3:10-11; 2:17; 5:2) by the divine life received through the divine birth (2:29; 4:7).
To preserve this abiding in the divine fellowship, three main negative things need to be dealt with. The first is sin, which is lawlessness and unrighteousness (1:7—2:6; 3:4-10; 5:16-18). The second is the world, which is composed of the lust of the flesh, the lust of the eyes, and the vainglory of this life (2:15-17; 4:3-5; 5:4-5, 19). The last is idols, which are the heretical substitutes for the genuine God and the vain replacements of the real God (5:21). These three categories of exceedingly evil things are weapons used by the evil one, the Devil, to frustrate, harm, and, if possible, even annihilate our abiding in the divine fellowship. The safeguard against his evil doing is our divine birth with the divine life (5:18), and, based upon the fact that the Son of God has through His death on the cross destroyed the works of the Devil (3:8), we overcome him by the word of God that abides in us (2:14). In virtue of our divine birth, we also overcome his evil world by our faith in the Son of God (5:4-5). Moreover, our divine birth with the divine seed sown into our inner being enables us not to live habitually in sin (3:9; 5:18), because Christ has taken away sins through His death in the flesh (3:5). In case we sin occasionally, we have our Paraclete as our propitiation to care for our case before our Father God (2:1-2), and the Son’s everlasting efficacious blood cleanses us (1:7). Such a revelation is the basic and substantial element of the apostle’s mending ministry.