1 Peter 1:22

purified . . . in obeying the truth--Greek, "in your (or 'the') obedience of (that is, 'to') the truth (the Gospel way of salvation)," that is, in the fact of your believing. Faith purifies the heart as giving it the only pure motive, love to God (Act 15:9; Rom 1:5, "obedience to the faith"). through the Spirit--omitted in the oldest manuscripts. The Holy Spirit is the purifier by bestowing the obedience of faith (Pe1 1:2; Co1 12:3). unto--with a view to: the proper result of the purifying of your hearts by faith. "For what end must we lead a chaste life? That we may thereby be saved? No: but for this, that we may serve our neighbor" [LUTHER]. unfeigned-- Pe1 2:1-2, "laying aside . . . hypocrisies . . . sincere." love of the brethren--that is, of Christians. Brotherly love is distinct from common love. "The Christian loves primarily those in Christ; secondarily, all who might be in Christ, namely, all men, as Christ as man died for all, and as he hopes that they, too, may become his Christian brethren" [STEIGER]. BENGEL remarks that as here, so in Pe2 1:5-7, "brotherly love" is preceded by the purifying graces, "faith, knowledge, and godliness," &c. Love to the brethren is the evidence of our regeneration and justification by faith. love one another--When the purifying by faith into love of the brethren has formed the habit, then the act follows, so that the "love" is at once habit and act.

— Jamieson-Fausset-Brown Commentary (public domain)