1 John 5:12
12 He that hath the Son hath life; and he that hath not the Son of God hath not life.
Possessing Christ, the Son of God, is to possess life eternal. Conversely, rejection of Christ means to live under the sentence of death, without having the eternal life that Christ alone offers. The Son of God Himself proclaimed in John 3:36, “He that believeth on the Son hath everlasting life: and he that believeth not the Son shall not see life; but the wrath of God abideth on him.” He again said in John 5:24, “Verily, verily, I say unto you, He that heareth my word, and believeth on him that sent me, hath everlasting life, and shall not come into condemnation; but is passed from death unto life.”
There is no reason to doubt if those who have Christ, the Son of God, have possession of eternal life. Those who have Christ are those who live by faith in Christ. Their lives show that they do possess Christ by faith. They do not behave like those who reject or have no knowledge of Christ. Their faith in Christ will be evident in their lives. If they ever fail to express their faith, being overcome with temptations, they will repent and renew their faith and walk again in the ways of Christ. Their repentance and renewal will prove their possession of life which the Son of God has given to them.
Those who have Christ will have the life that He gives, not the life that the world and the devil have prepared for those who seek to possess the world. The present lives of those who have Christ will certainly manifest all the characteristics of the life that is in Him.
The apostle John has given us much evidence of the spiritual life possessed by those who possess Christ. Let us consider some of the proofs mentioned by John. The first proof is that they obey His commandments (cf. 1 John 2:3-4). Secondly, they live a righteous life (cf. 1 John 2:29). Thirdly, they do not habitually commit sin (cf. 1 John 3:9; 5:18). Fourthly, they love the brethren (1 John 3:14; 4:7). The fifth, and by no means the last, proof is that they overcome the world (1 John 5:4).
The life that Christ gives to those who receive Him is not just life in heaven, but also a present life of Christ-likeness. While a Christ-like life proves that one has Christ, a worldly life demonstrates that one has rejected Christ. Let us delight in the life which Christ gives and dismiss the deadness of worldliness and sin.