And we have this commandment from Him: Whoever loves God must love his brother as well.
Καὶ ταύτην τὴν ἐντολὴν ἔχομεν ἀπ᾿ αὐτοῦ, ἵνα ὁ ἀγαπῶν τὸν Θεόν, ἀγαπᾷ καὶ τὸν ἀδελφὸν αὐτοῦ.