Seeing you have purified your souls in your obedience to the truth through the Spirit in sincere brotherly affection, love one another from the heart fervently:
Unto unfeigned love of the brethren - The effect of the influence of the Holy Spirit in applying the truth has been to produce sincere love to all who are true Christians. Compare the John 13:34 note; 1 Thessalonians 4:9 note. See also 1 John 3:14-18.