First John reveals unrest in the early church. False teachers were leading many saints astray from the truth (see 1 John 2:26; 1 John 37). The erring caused such stirs in the churches of Christ that splits occurred and they eventually left the faithful (see 1 John 2:18-19). Whether these erring brethren were Gnostics, opinion driven people, or those who invented religious ideas that became their personal convicted truths matters not. What mattered to John, as he wrote by divine inspiration, was that the true child of God let the anointing from the Holy One abide in their hearts (i.e., absolute divine revelation or truth) (see 1 John 2:20). John wrote, "And as for you, the anointing which ye received of him abides in you, and ye need not that any one teach you; but as his anointing teaches you concerning all things, and is true, and is no lie, and even as it taught you, ye abide in him" (1 John 2:27). Eternal life with the heavenly Father would only be possible through Christ's forgiving blood and man's faithful obedience to truth (see 1 John 1:1-4; 1 John 2:1-2, 1 John 25; 1 John 5:11, 1 John 5:13). No Christian needed to be taught a new gospel!
There were two things standing in the way of the saint's eternal life with the heavenly Father. First, John explains the position sin places one in. Sin, in any form, is not ok no matter what others may say. John writes, "My little children, these things write I unto you that ye may not sin. And if any man sin, we have an Advocate with the Father, Jesus Christ the righteous:" (1 John 2:1 John discusses two areas of sin in this short epistle. First, there is the sin of worldliness; i.e., the lust of the flesh, eyes, and vainglory of life (see 1 John 2:15-17). Secondly, there is the sin of false teaching (see 1 John 2:18-23; 1 John 4:1-3). The other thing that stood in the way of the saints spending eternity with God was a lack of love for their fellow brethren (1 John 2:9-11; 1 John 3:16-18; 1 John 4:7-11, 1 John 4:20-21).
As it was not ok for Cain to kill Able, it is not ok for one brother not to love another brother (see 1 John 3:11-12). To love your brother is to care about their spiritual and physical well being (1 John 3:16-17; see 3 John 19). To love your brother is to be kind, patient, selfless, and 11 other traits that Paul reveals at 1 Corinthians 13:1-8.
The solution to the problem of sin and a lack of love was that the saints let the word of God abide in their hearts (1 John 224-28; 1 John 4:12-13, 16). When the word of God dwells within one fellowship with the Father occurs. All that such a one does is dictated by the word of God. The word of God becomes one with the mind of the saint so that keeping the commandments of God becomes second nature rather than a grievous matter (see 1 John 5:3). When such a one sins they are bothered so badly that they cannot function till they go to God in prayer asking for forgiveness (see 1 John 1:8-10). Such an approach to life sets the true saint of God apart from the sinful world and opinionated personally convicted brethren (see 1 John 3:10). The world recognizes this difference as they see our conscience bothered by sin (see 1 John 3:13; 1 John 4:5). The saint of God also notices this difference (1 John 5:19). John, by divine inspiration, sets a high standard for all Christians to follow. Each of the children of God must become as God in holiness, love, and righteousness (see 1 John 1:6; 1 John 2:6; 1 John 3:3,1 John 3:5,1 John 3:7; 1 John 4:17). We may all experience victory over Satan and sin yet it will take a mind that is saturated with truth (1 John 4:4; 1 John 5:4-5).
Brethren, cast the shackles of Satan off of you (1 John 5:21 Many have been taught a gospel of some preacher's personal convictions rather than truth as revealed in God's word. You have let these early principles become a tradition that supersedes the word of God (see Matthew 15:19). Some have held on to childhood convictions at the expense of actual truth. The apostle John tells us that if you hold to, these personal convictions or opinions rather than truth you are of the devil and antichrist (1 John 3:8; 4:3). You will eventually separate yourselves from the true faithful but such a separation will only give you temporary peace (see 1 John 2:18-19). It will be, and always has been, the distinctive preaching of truth that drives the erring from the flock of the faithful (Matthew 15:12-14; John 6:60-66). John C Robertson