John Calvin Commentary 1 John 5:1

"Whosoever believeth that Jesus is the Christ is begotten of God: and whosoever loveth him that begat loveth him also that is begotten of him." — 1 John 5:1 (ASV)

Whosoever believeth. He confirms by another reason that faith and brotherly love are united; for since God regenerates us by faith, He must necessarily be loved by us as a Father, and this love embraces all His children. Then faith cannot be separated from love.

The first truth is that all who are born of God believe that Jesus is the Christ; where, again, you see that Christ alone is set forth as the object of faith, as in Him faith finds righteousness, life, and every blessing that can be desired, and God in all that He is. Hence, the only true way of believing is when we direct our minds to Him. Besides, to believe that He is the Christ is to hope from Him all those things which have been promised concerning the Messiah.

Nor is the title Christ given Him here without reason, for it designates the office to which He was appointed by the Father. As, under the Law, the full restoration of all things, righteousness, and happiness were promised through the Messiah, so today the whole of this is more clearly set forth in the gospel. Then Jesus cannot be received as Christ unless salvation is sought from Him, since for this purpose He was sent by the Father and is daily offered to us.

Hence, the Apostle declares that all those who really believe have been born of God; for faith is far above the reach of the human mind, so that we must be drawn to Christ by our heavenly Father; for none of us can ascend to Him by our own strength.

And this is what the Apostle teaches us in His Gospel, when he says that those who believe in the name of the Only-begotten, were not born of blood nor of the flesh (John 1:13). And Paul says that we are endowed not with the spirit of this world, but with the Spirit that is from God, that we may know the things given us by him (1 Corinthians 2:12).

For eye hath not seen, nor ear heard, nor the mind conceived, the reward laid up for those who love God; but the Spirit alone penetrates into this mystery. And further, as Christ is given to us for sanctification and brings with it the Spirit of regeneration, in short, as He unites us to His own body, it is also another reason why no one can have faith unless he is born of God.

Loveth him also that is begotten of him. Augustine and some others of the ancients have applied this to Christ, but not correctly. For though the Apostle uses the singular number, yet he includes all the faithful; and the context plainly shows that his purpose was none other than to trace brotherly love to faith as its fountain. It is, indeed, an argument drawn from the common course of nature; but what is seen among men is transferred to God.

But we must observe that the Apostle does not speak only of the faithful and pass by those who are outside, as though the former alone are to be loved, and no care or account is to be taken of the latter; but he teaches us, as it were, by this first exercise to love all without exception, when he bids us to make a beginning with the godly.