1 John 2:29

‘If you know (oida - in the mind) that he is righteous, you know (ginosko - experientially) that every one also who does righteousness is begotten of him.'

And because they know Him they know Him as the Righteous One. They know Him as the One Who, because it was His delight, fully kept, and requires the joyous keeping of, God's will as seen in His commandments and His Law (Hebrews 10:7; Hebrews 10:9; Romans 7:22; Psalms 1:2; Psalms 40:8; Psalms 112:1; Psalms 119:16 and often in that Psalm. Note also in Psalms 119 the constant claim to love His Law). Thus they know that one test of who is begotten of Him is that they live righteously, that they ‘do His commandments', and that those who joyously and gladly live righteously, that is in accordance with God's Law, do so because they are begotten of Him. True righteousness can only result from God's begetting. This contrasts with those who struggled to keep the Law in order to gain merit, for whom it was a burden not a joy.

‘Begotten of Him.' In context this means ‘begotten of Christ'. 1 John 2:28 has specifically had Christ in mind, and 1 John 3:1 opens with a new subject, ‘the Father'. The normal expression for John is ‘begotten of God' (1 John 3:9; 1 John 4:7; 1 John 5:1; 1 John 5:4; 1 John 5:18 see also John 1:12). But Jesus could speak of men being ‘born of the Spirit' (John 3:6; John 3:8). And He Himself said that as the Son He ‘had life in Himself' (John 5:26), and that it is His voice that will raise the dead, and those who hear will live (John 5:25), speaking there of the new birth to eternal life (1 John 2:24). ‘Begotten of Christ' sealed the emphasis that John has been putting on the close working relationship between the Son and the Father. Once again it illustrates how closely John parallels Jesus Christ with God.