1 Peter 4:8, Above all, keep loving one another earnestly, since love covers a multitude of sins.
Luther says it better than I ever could, “We love to beautify and decorate ourselves and to see what is good in us, tickling ourselves with it as if it belonged to us. In order to maintain our exclusive claim to beauty, we ignore and leave out of sight the good there is in our neighbour” (The Sermon on the Mount, LW 21:214-215). We fatten our heads with thoughts of self-glory whilst we belittle our neighbour for the littlest pimple, too thick of a waistline, and too dark of a past even though Christ has forgiven and healed him. Such pedantic absurdity is not Christian love.
Luther continues, “So it is that we overlook our own vices, which are all over us, while we fail to see anything good about other people.” Whether perfection of skin, body shape, or conduct, we think ourselves better even whilst we judge ourselves. “At least I’m not as bad as he is,” we say. Thus, we treat them with contempt and dishonour. This is sin.
Love, conversely, covers a multitude of sins in three ways: 1) By loving our neighbour in spite of their bodily imperfections and character flaws, we do not sin against them and thus hinder them from sinning against us (cf. Matthew 7:2); 2) by loving our neighbour, we forgive their sins and offer grace just as Christ has forgiven them and is gracious toward them; and 3) love does not overlook the neighbour’s sin or endorse it, but calls it out and strives to bring the neighbour to repentance and trust in Christ.