John Calvin Commentary 1 John 2:29

"If ye know that he is righteous, ye know that every one also that doeth righteousness is begotten of him." — 1 John 2:29 (ASV)

If you know that he is righteous, he again passes on to exhortations, so that he mingles these continually with doctrine throughout the Epistle; but he proves by many arguments that faith is necessarily connected with a holy and pure life.

The first argument is that we are spiritually begotten after the likeness of Christ; it therefore follows that no one is born of Christ but one who lives righteously. At the same time, it is uncertain whether he means Christ or God when he says that those who are born of him do righteousness. It is certainly a mode of speaking used in Scripture, that we are born of God in Christ; but there is nothing inconsistent in the other view, that those who are renewed by his Spirit are born of Christ.