Theophylact of Ohrid

Therefore he adds: "in this is love," that is, by this it is proved that God is love. Then, showing the surpassing quality of God's love, he says: God did this, that is, gave up His own Son for us, not because we loved Him, but He was the first to begin bestowing benefits upon us out of love and sent His Son, and not only sent Him, but also by His own blood accomplished the cleansing of our sins.

Commentary on 1 John ↗

Augustine of Hippo

This we have said in the case where the things done are similar. In the case where they are diverse, we find a man by charity made fierce; and by iniquity made winningly gentle. A father beats a boy, and a boy-stealer caresses. If thou name the two things, blows and caresses, who would not choose the caresses, and decline the blows? If thou mark the persons, it is charity that beats, iniquity that caresses. See what we are insisting upon; that the deeds of men are only discerned by the root of charity. …

Ten Homilies on 1 John 7 ↗

Bede

And he sent his Son to be the propitiation, etc. And this is the greatest sign of divine love for us, because when we did not yet know how to ask him for forgiveness for our sins, he sent his Son to us, who, to those believing in him, would grant pardon freely and call us to the fellowship of paternal glory. In some Codices, this verse is read thus: And he sent his Son to be the altar sacrifice for our sins. The altar sacrifice means a sacrificer. …

Commentary on the Catholic Epistles ↗

Bernard of Clairvaux

Good Jesus, the chalice you drank, the price of our redemption, makes me love you more than all the rest. This alone would be enough to claim our love. This, I say, is what wins our love so sweetly, justly demands it, firmly binds it, deeply affects it. Our Savior had to toil so hard in this, in fact in making the whole world the Creator did not labor so much. Then he spoke and they were made; he commanded and they were created. …

Sermons on the Song of Songs, Sermon 20 ↗