John Calvin Commentary 1 John 3:7

"[My] little children, let no man lead you astray: he that doeth righteousness is righteous, even as he is righteous:" — 1 John 3:7 (ASV)

He that doeth righteousness. The Apostle shows here that newness of life is testified by good works; nor does that likeness of which he has spoken—that is, between Christ and his members—appear, except through the fruits they bring forth. It is as if he had said, "Since it is fitting for us to be conformed to Christ, the truth and evidence of this must appear in our life." The exhortation is the same as that of Paul in Galatians: If you live in the Spirit, walk also in the Spirit (Galatians 5:25).

For many would gladly persuade themselves that they have this righteousness buried in their hearts, while iniquity evidently occupies their feet, and hands, and tongue, and eyes.