Matthew Henry Commentary Ephesians 4:17-24

"This I say therefore, and testify in the Lord, that ye no longer walk as the Gentiles also walk, in the vanity of their mind, being darkened in their understanding, alienated from the life of God, because of the ignorance that is in them, because of the hardening of their heart; who being past feeling gave themselves up to lasciviousness, to work all uncleanness with greediness. But ye did not so learn Christ; if so be that ye heard him, and were taught in him, even as truth is in Jesus: that ye put away, as concerning your former manner of life, the old man, that waxeth corrupt after the lusts of deceit; and that ye be renewed in the spirit of your mind, and put on the new man, that after God hath been created in righteousness and holiness of truth." — Ephesians 4:17-24 (ASV)

The apostle charged the Ephesians in the name and by the authority of the Lord Jesus that having professed the gospel, they should not be like the unconverted Gentiles, who walked in futile thinking and worldly desires. Do men not, everywhere, walk in the futility of their minds? Must we not then urge the distinction between real and nominal Christians?

They were devoid of all saving knowledge; they sat in darkness and loved it rather than light. They had a dislike and hatred for a life of holiness, which is not only the way of life God requires and approves, and by which we live to him, but which also has some likeness to God himself in his purity, righteousness, truth, and goodness. The truth of Christ appears in its beauty and power when it appears as it is in Jesus.

The corrupt nature is called a man; like the human body, it is of diverse parts, supporting and strengthening one another. Sinful desires are deceitful lusts; they promise men happiness, but render them more miserable, and bring them to destruction if not subdued and mortified.

Therefore, these must be put off as an old garment, a filthy garment; they must be subdued and mortified. But it is not enough to shake off corrupt principles; we must have gracious ones.

By 'the new man,' is meant the new nature, the new creature, directed by a new principle—namely, regenerating grace—enabling a man to lead a new life of righteousness and holiness. This is created, or brought forth, by God's almighty power.