1 John 5:2

“By this we know that we are the children God, &c.] The Ethiopic version reads, “by this know that we love God”; which, in connection with what follows, makes a tautology, and is a proving “idem per idem”: whereas the apostle's view is to show when love to the saints is right; and that is, when we love God, and keep his commandments: love to the brethren may arise from such a cause, as may show that it is not brotherly love, or of a spiritual kind; it may arise from natural relation, or civil friendship, or from a benefit or favour received from them, and from some natural external excellency seen in them; and a man may do acts of love and kindness to the brethren, from what may be called…”

“By--Greek, "In." As our love to the brethren is the sign and test of our love to God, so (John here says) our love to God (tested by our "keeping his commandments") is, conversely, the ground and only true basis of love to our brother. we know--John means here, not the outward criteria of genuine brotherly love, but the inward spiritual criteria of it, consciousness of love to God manifested in a hearty keeping of His commandments. When we have this inwardly and outwardly confirmed love to God, we can know assuredly that we truly love the children of God. "Love to one's brother is prior, according to the order of nature (see on Jo1 4:20); love to God is so, according to the order of grace…”

“By this we know that we love the children of God ... - This is repeating the same truth in another form. “As it is universally true that if we love Him who has begotten us, we shall also love His children, or our Christian brethren, so it is true also that if we love His children it will follow that we love Him.” In other places, the apostle says that we may know that we love God if we love those who bear His image, 1 John 3:14. He here says, that there is another way of determining what we are. We may have undoubted evidence that we love God, and from that, as the basis of an argument, we may infer that we have true love to His children. Of the fact that we may have evidence that we love…”

“Hereby we know - This is a plain proof. That we love the children of God - As his children. 1 John 5:3”

“Jo1 3:22-24, Jo1 4:21; Joh 13:34, Joh 13:35, Joh 15:17 1 John 5:3”