The repetition of the word "righteous" is to be noted. There seems to be an intimation that sin is alien to the character of a "righteous" man. Compare 1 John 3:7-9.

Nevertheless, if thou warn the righteous man,.... Every righteous man, that is so in a judgment of charity, whether truly righteous or not, which the event shows; who should be warned not to trust in their own righteousness, but to depend on the righteousness of Christ; that they be careful to maintain good works, to avoid sin, and live holy lives and conversations, as follows:

that the righteous sin not; not that there is any just man that does good, and sins not; the best of men are often sinning in thought, word, or deed; but he is to be warned that he does not continue in sin, and lead a sinful coups of life; which is contrary to his character, and to his faith in Christ for righteousness, which is attended with good works:

and he doth not sin; the warning and exhortation given him having so good an effect, through the power of divine grace, as to be a means of preserving him from a vain conversation:

he shall surely live; spiritually and comfortably now, and eternally hereafter:

because he is warned; that being a means, and with the divine blessing taking effect:

also thou hast delivered thy soul; See Gill on Ezekiel 3:19.

Nevertheless if thou warn the righteous man, that the righteous sin not, and he doth not sin, he shall surely live, because he is warned; also thou hast delivered thy soul.

3:12-21 This mission made the holy angels rejoice. All this was to convince Ezekiel, that the God who sent him had power to bear him out in his work. He was overwhelmed with grief for the sins and miseries of his people, and overpowered by the glory of the vision he had seen. And however retirement, meditation, and communion with God may be sweet, the servant of the Lord must prepare to serve his generation. The Lord told the prophet he had appointed him a watchman to the house of Israel. If we warn the wicked, we are not chargeable with their ruin. Though such passages refer to the national covenant made with Israel, they are equally to be applied to the final state of all men under every dispensation. We are not only to encourage and comfort those who appear to be righteous, but they are to be warned, for many have grown high-minded and secure, have fallen, and even died in their sins. Surely then the hearers of the gospel should desire warnings, and even reproofs.