And we have this commandment from Him: Whoever loves God must love his brother as well.
Besides the argument (Jo1 4:20) from the common feeling of men, he here adds a stronger one from God's express commandment (Mat 22:39). He who loves, will do what the object of his love wishes. he who loveth God--he who wishes to be regarded by God as loving Him. Next: 1 John Chapter 5
And this commandment have we from him, That he who loveth God love his brother also. (17) A second reason, why God cannot be hated and our neighbour loved, because this same lawmaker commanded us both to love him and our neighbour.
Verse 21. And this commandment have we from him. That is, the command to love a brother is as obligatory as that to love God. If one is obeyed, the other ought to be also; if a man feels that one is binding on him, he should feel that the other is also; and he can never have evidence that he is a true Christian...