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, unless he manifests love to his brethren as well as love to God. See the notes at James 2:10.
That he who loveth God love his brother also - See the notes at John 13:34-35. Compare John 15:12, John 15:17.