1 Peter 1:22

Seeing ye have purified your souls
The apostle passes to another exhortation, namely, to brotherly love; the ground of which he makes to be, the purification of their souls; and which supposes that they had been impure; and indeed, their whole persons, souls and bodies, were so by nature; even all the members of their bodies, and all the powers and faculties of their souls: it is internal purity, purity of the heart, that is here particularly respected; though not to the exclusion of outward purity, for where there is the former, there will be the latter; but there may be an external purity, where there is not the inward one: this the apostle ascribes to the saints themselves, but not without the grace of God, the blood of Christ, and the operations of his Spirit; as appears by a following clause; but they are said to purify themselves, inasmuch as having the grace of faith bestowed on them, they were enabled, under the influences of the Spirit of God, to exercise it on the blood of Christ, which cleanses from all sin:

in obeying the truth;
of the Gospel, by receiving, believing, and embracing it in the love of it; which teaches outward purity, and is a means in the hand of the spirit of inward purity, and of directing to the purifying blood of Jesus, who sanctifies and cleanses by the word:

through the Spirit;
this clause is left out in the Alexandrian copy, and some others, and in the Vulgate Latin, Syriac, and Ethiopic versions, but is in the Arabic version, and ought to be retained; for, as Christ died to purify to himself a peculiar people, the Spirit of Christ does from him purify the heart by faith in his blood; by sprinkling that on the conscience, and by leading the faith of God's people to the fountain of it, to wash it for sin, and for uncleanness; even both their consciences and their conversation, garments; whereby they obtain inward and outward purity:

unto unfeigned love of the brethren;
which is the end of sanctification, and an evidence of it; when the saints are loved as brethren, and because such; and with a love without dissimulation, not in word and in tongue only, but in deed and in truth: this being the case, the exhortation follows:

[see that ye] love one another with a pure heart fervently:
this is Christ's new commandment, and the evidence of regeneration; a distinguishing badge of Christianity, and without which all profession of religion is a vain and empty thing: this should he mutual and cordial; should proceed from the heart, and from an heart sprinkled from an evil conscience; and should be with warmth and fervency, and not with coldness and indifference; though the word here used, (ektenwv) , may not only design the intenseness of it, but the extensiveness of it also; as that it should reach to all the saints, the poor as well as the rich, and the lesser as well as the greater and more knowing believers; and likewise may denote the continuance of it; it ought to be continually exercised, and to last always; and so the Arabic version renders it, "with a perpetual love".