1 John 4:10

Herein is love
The love of God, free love, love that cannot be matched: herein it is manifested, as before; this is a clear evidence of it, an undoubted proof, and puts it out of all question:

not that we loved God:
the love of God is antecedent to the love of his people; it was when theirs was not; when they were without love to him, yea, enemies in their minds, by wicked works, and even enmity itself, and therefore was not procured by theirs; but on the contrary, their love to him is caused by his love to them; hence his love, and a continuance in it, do not depend on theirs; nor does it vary according to theirs; wherefore there is good reason to believe it will continue, and never be removed; and this shows the sovereignty and freeness of the love of God, and that it is surprising and matchless:

but that he loved us;
that is, God; and so the Syriac version reads, "but that God himself loved us". The Vulgate Latin version adds, first, as in ( 1 John 4:19 ) ; the instance of this love follows:

and sent his Son [to be] the propitiation for our sins:
this is a subordinate end to the other, mentioned in ( 1 John 4:9 ) ; for, in order that sinful men may possess everlasting life and happiness, it is necessary that their sins be expiated, or atonement be made for them, which is meant by Christ's being a propitiation for them; that the justice of God should be satisfied; that peace and righteousness, or love and justice, should be reconciled together; and kiss each other; and that all obstructions be removed out of the way of the enjoyment of life, which are brought in by sin; and that the wrath of God, which sin deserved, be averted or appeased, according to our sense apprehension of it; for otherwise the love of God people is from everlasting, and is unchangeable, never alters, or never changes from love to wrath, or from wrath to love; nor is the love of God procured by the satisfaction and sacrifice of Christ, which are the effects of it; but hereby the way is laid open for the display of it, and the application of its effects, in a way consistent with the law and justice of God. This phrase is expressive of the great love of Christ to his people, and of his substitution in their room and stead; and so it is used among the Jews for a substitution in the room of others, (wtbha bwrl) , "to express the greatness of love" ^F21; (See Gill on Romans 3:25) and (See Gill on Romans 9:3).