1 Peter 1:22

22 Since you have in obedience to the truth purified your souls for a sincere love of the brethren, fervently love one another from the heart,

Here we have an obvious break in the narrative, where Peter turns more toward application. In verses 13-17 he encourages the reader toward obedience and holiness. Now he sharpens the scope toward love of the brethren. As Peter put it, in their obedience to the truth (as obedient Christians) they acted to purify their souls so that they were able to fervently love one another from the heart.