1Jn. 2:25- "And this is the promise that He has promised us--eternal life."
Jesus said that Satan is a liar and the father of lies. (Jn. 8:44) Satan tells us many lies. But what is Satan's greatest lie? That Jesus is not the Son of God, that Jesus is not the Christ.
There is a difference between a created being and a begotten one. Man is a created being. When humans reproduce children, they beget children. Humans reproduce, or beget, of their own kind. None of us were begotten of the heavenly Father because we are not of the same kind as the Father. We were created by the Father out of material not of His own being, out of material He created out of nothing. Jesus is the Father's only begotten Son, He is of the same kind as the Father. Jesus and the Father are one. If Jesus is not the only begotten Son of the Father, then His sacrifice for our sins would have been for nothing. Only a perfect sacrifice would meet the demands of the Father's justice, and if Jesus was merely human, not the only begotten Son, then He would not be the perfect sacrifice, for He would be tainted by sin as well. If this were the case, Jesus would not be the Christ, the Messiah sent from the Father.
Those that deny that Jesus is the Christ, John calls anti Christ. (1Jn. 2:22) If we abide in the truth that Jesus is the Christ, which we heard from the beginning, then we abide in the Father and the Son. (v. 23-24) Today there are some who believe truth or doctrine is not as important as doing what Jesus did. Their favorite quotation is from St. Francis of Assisi: "Preach the Gospel at all times and if necessary use words." Yet if we abide in the truth, we abide in both the Father and the Son. Those who deny the doctrines concerning the Son does not have the Father. (v. 23) Abiding in both the Father and the Son qualifies us to receive the promise of eternal life. (v. 25) We don't understand much concerning the Trinity; there is so much about it that is a mystery. Yet all who do put their faith in Christ are taught by the Holy Spirit that the doctrine of the Trinity is true. (v. 27) To abide in Christ is not only to seek to be Christian in action, but also to be truthful in knowing and teaching others who Christ really is. We cannot abide in His person without abiding in correct doctrine concerning Him. We cannot have the eternal life promise to us if we do not abide in correct doctrine.