So Christ urges us in the Gospels,
Matthew 22:37-39 37 And he said to him, “You shall love the Lord your God with all your heart and with all your soul and with all your mind. 38 This is the great and first commandment. 39 And a second is like it: You shall love your neighbor as yourself.
Paul, carries this law to all the churches; Galatians 5:14 14 For the whole law is fulfilled in one word: “You shall love your neighbor as yourself.”
James repeats it as a royal law: James 2:8 8 If you really fulfill the royal law according to the Scripture, “You shall love your neighbor as yourself,” you are doing well.
But what does it mean? How do we do it? Here is Herman Witsius’s summary
For, he who loves God, cannot but love His image too, in which he clearly views express characters of the Deity, and not a small degree of the brightness of his glory. Again, whoever loves God, will, by virtue of that love, seriously wish, desire, study, and as much as in him lies, be careful, that his neighbour, as well as himself, be under God, in God, and for God, and all he has, be for his glory. Again, whoever loves God, will make it his business, that God may appear every way admirable and glorious; and as he appears such most eminently in the sanctification and happiness of men, 2 Thess. 1. 10. he will exert himself to the utmost, that his neighbour make advances to holiness and happiness. Finally, whoever sincerelv loves God, will never think he loves and glorifies him enough; such excellencies he discovers in him, sees his name illustrious, and so exalted above all praise, as to long, that all mankind, nay all creatures, should join him in loving and celebrating the infinite perfections of God. But this is the most faithful and pure love of our neighbour, to seek that God may be glorified in him, and he himself be for the glory of God. Hence it appears, that the love of our neighbour is inseparably connected with that of God, If therefore it flows from the nature of God, to enjoin us the love of himself, as was just proved; it must likewise flow from the nature of God to enjoin us the love of our neighbour.
Herman Witsius, The Enconomy of the Covenants (Grand Rapids, Reformation Hertage Books, 2010) Volume 1:1:3:66.