John begins with a passionate exhortation to his readers to “love one another,” a phrase which is repeated three times in verses 7, 11, and 12. This is his great concern, and the reasons for that concern are given in connection with this threefold repetition. The first reason is that love is of God’s own nature; therefore, Christians are to “love one another.” The second reason concerns God’s gift in Christ; therefore, Christians are to “love one another.” The third reason is God’s present activity in and through His people; for this reason, too, Christians are to “love one another.” Up to this point love has been seen mostly as a duty binding upon believers. Now it is seen for what it most truly is, a driving disposition arising out of the divine nature which by God’s grace is now also within the Christian.
The first reason why Christians must love other Christians is that the very nature of God is love and that this demands it. John states this in two forms, saying that “love is of God” and that “God is love.” The first of these indicates that God is the source of all love. If this is so, however, the one who loves must love with that love which comes from God and, therefore, he must be born of Him. If he does not love, he does not know God. The second form of John’s statement is that “God is love.” This is more profound than the former, for it regards love not merely as a gift or attribute of God but in the deepest sense as God’s own nature. It is to be taken alongside those two other unequivocal statements of John which tell us that “God is spirit” (John 4:24) and that “God is light” (1 John 1:5).
John links love to the nature of God in a very subtle way in these verses, and this should not be missed. It is seen in the fact that each of these statements regarding love and our need to love is linked to one of the persons of the Trinity, so that the entire Trinity is involved. In verses 7 and 8 the reference is to God the Father; it is this that we have just been considering. In verses 9-11 the reference is primarily to God the Son. God loved us so much that He died for us, and therefore we should love one another. Finally, in verse 12, in the phrase “God abides in us,” the reference is to God the Holy Spirit; and again the conclusion is the same: love one another. In other words, God the Father is love, God the Son is love, God the Spirit is love. Therefore, if we know the God who is Father, Son, and Holy Spirit, we will love. It is difficult to see how the matter could be made simpler than this or more pressing upon the conscience of the Christian.