1 Peter 1:22

The apostle had appealed to their conscious knowledge of redemption by that which is of all things most precious to God—the blood of Christ as of a lamb unblemished and spotless. And if it was eternally before God, however late in accomplishment, God's raising Christ from the dead had through Him so acted on them, that their faith and hope were in God. From Him they looked for all good, and nothing but good, henceforth and forever. He has now further considerations of the greatest weight in urging the saints to mutual love; for this is only secondary to receiving Christ and the truth, without which is no love according to God's nature.
“Purified your souls as ye have in your obedience to the truth1 unto brotherly affection unfeigned, love one another out of a pure2 heart fervently” (vers. 22).
Thus the saints are authoritatively taught the true source of their purification. It is from God as certainly as it is to God. It is not ritual which could not purge the conscience, but in the fullest sense personal; it was not in their habits only, or even their thoughts and affections. They had purified “their souls,” that is, their inner selves in all extent. For a man's soul is essentially the seat of his conscious individuality, of his will, of his responsibility to God. His inner capacity is in his “spirit,” for or about which he is as responsible as for the things done through the body as the outer instrument; but his responsibility lies in the soul. Soul and spirit however are so closely joined, that but one of the two generally is named, as here. Only the one which is named in scripture, though not excluding the other, is always strictly correct and has its proper force. On the other hand men and in particular philosophers, as they shrink from facing their responsibility to God, constantly incline to count the “I” to be in the “spirit,” of which they are proud, rather than in the “soul,” awakening thoughts which they do not relish. What depths of sin and shame has not man's will led him into?
But those to whom the Epistle is addressed had no more hesitation in owning the truth as to themselves than the apostle had in crediting them with the grace in question. It is not a wish or a prayer that they should be purified, but rather is assumed as a settled fact, as surely as they were faithful. This is said in no levity, nor does it imply the least license; save that they were still passing through a desert world, exposed to a sleepless enemy. Hence were they dependent on their unseen God and Father, as He is unfailingly faithful to such. But the call to love one another is manifestly grounded on the assurance that they had purified their souls already; which involves the responsibility of continual consistency with this state of purity, and of self-judgment in case of failure. It is the regular Christian standing, which may be varied in the form of expression; but it meets us substantially in every apostolic Epistle.
Hence our apostle averred the like grace for the believing Gentiles, when he pleaded the cause of their liberty against Pharisaic brethren who sought to put them under law: “And the heart-knowing God bore them witness, giving the Holy Spirit just as to us also, and made no difference between us and them, having cleansed their hearts by faith.” As in Acts 15:8, 98And God, which knoweth the hearts, bare them witness, giving them the Holy Ghost, even as he did unto us; 9And put no difference between us and them, purifying their hearts by faith. (Acts 15:8‑9) “faith” is stated to be the subjective means, our scripture says yet more that it was by the Jews' “obeying the truth” objectively put before them. “Obedience to the truth” is but another and fuller way of expressing their faith. To have a solid and divine character there must be subjection to the truth.
Further, the purification of their souls is next shown to be “unto brotherly affection unfeigned.” Before we have purified our souls, there is everything not only to hinder such affection but to render it impossible. Sin, darkness, self, fleshly and worldly lusts, and under Satan's power make men more and more miserable, relieved only by pleasures as vain as the religious efforts of a bad conscience in lieu of happiness. How deep the ruin of the fall! God good and holy, whom man gave up and lost, was replaced by the liar and the murderer! Cain is the firstborn of Adam and Eve: what a witness of natural religion and of brotherly affection! Abel testifies to grace by faith. By birth we are like the one, by new birth our part is with the other. “By faith Abel offered to God a mere excellent sacrifice than Cain.”
God justified us by faith, giving us redemption through the blood of Jesus. Not otherwise were our souls purged, and thereby are we fitted for brotherly affection, such as God looks for in Christians. In ordinary circumstances any other feeling would dishonor and in effect deny the relationship which grace has established for our present and mutual recognition. Scripture clearly lays down the exceptional cases, and how we ought then to behave; but we need not now say more about it. This is the Lord's new commandment. By this, said He, shall all know that ye are my disciples, if ye have love among one another.
So the Spirit guards against mere forms or words by qualifying the brotherly affection for which their souls were purified as “unfeigned.” Pretense to a good that is not genuinely felt is hateful to God, and unworthy of His child. Hence the value of cherishing the sense of His presence to be kept from hypocrisy in this way as in every other. Let us never forget His marvelous light into which He carried us out of darkness. “Know ye not,” says the apostle Paul, “that ye are God's temple, and the Spirit of God dwelleth in you”?
Hence the exhortation, which is not tautological as some have irreverently said, “Out of a pure heart love one another fervently,” or intensely. It is a simple charge that the object in view may be earnestly heeded. God's love to us is the spring of all our blessing, and never did it flow out so freely and fully as when man's sin proved how utterly undeserving he was, and no less wretched and helpless. Then it was, and at the lowest point, when God turned his evil in rejecting and slaying Christ, His Son, to the proof of His own all-over-coming goodness in making Him Who knew no sin to be sin for us, that we might become God's righteousness in Him. In the faith of Him and His sacrifice have we purified our souls, hitherto steeped in defilement, unto unfeigned brotherly affection. Let us love then the objects of the same divine love, who rest on the same sin-cleansing sacrifice. No doubt they were called to be holy throughout their course, because He Who called them is holy; but they were bound to love their brethren, not for any reasons of their own or for reasons in others, but “out of a pure heart” and “fervently “: had not God so felt and dealt with them? Even to heathen, when they believed in Christ, the apostle could write (1 Thess. 4:99But as touching brotherly love ye need not that I write unto you: for ye yourselves are taught of God to love one another. (1 Thessalonians 4:9)), “ye yourselves are taught of God to love one another.”