‘Whoever is begotten of God does no sin, because his seed abides in him, and he cannot sin, because he is begotten of God.'
For the plain fact is that if a man has been begotten of God, God's seed is within him. Begetting involves the planting of seed. And he who has been planted with God's seed has been made a partaker of the divine nature (2 Peter 1:4). The divine light and life is planted within, they are children of light (John 12:36; Ephesians 5:8). Thus there is that within them which militates against sin, and makes them abhor the thought of it. Such a person does not want to be a sinner. He cannot go on carelessly sinning, because he is begotten of God and has become a new creation (2 Corinthians 5:17). It is against what he now is. Sin has become something that is contrary to what he is as a new man. Something new within him begins to say ‘no' to sin.
‘His seed continues (abides) in Him.' Peter describes God's seed as incorruptible and lifegiving, and as related to His word, saying of Christians that they are, ‘begotten again, not of corruptible seed but of incorruptible, through the word of God which lives and abides for ever' (1 Peter 1:23 compare James 1:18). For the seed is sown through His word of power and comes forth to do His will (Isaiah 55:11), and achieves His will and continues for ever. Nothing can prevent its progress and the completeness of its success. That which is born of the flesh is flesh, and that which is born of the Spirit is Spirit (John 3:6 compare John 1:12-13). Thus the seed is the result of the work of the Spirit through His word. It is a principle of divine life planted within by God.
In the same way Jesus told the parable of the sower. The seed was sown. In some cases the seed was lost, it did not abide. But in the case of the good seed it continued, it flourished, it produced a harvest, in some thirtyfold, in some sixtyfold, and in some a hundredfold. Not all the good seed flourished equally, but all produced a harvest. For the good seed grows in a way that is beyond man's understanding and brings about God's will (Mark 4:27).
The ancient mind did not separate man's seed from wheat's seed as strictly as we might. All seed was seed. Thus the further jump to God placing His life-producing seed within man was not difficult.