John 1 v 12 But as many as received him, to them gave he power to become the sons of God, even to them that believe on his name: 13 Which were born, not of blood, nor of the will of the flesh, nor of the will of man, but of God.
In other words those who received him, that is received Jesus the incarnate Word by faith, received him because he had given them power to believe so that they could receive him by believing on him.
The Word was the source of this power to receive and become sons of God. Being thus empowered those who believed and received the Word were born of God. This empowerment is an action ascribed to God in verse 13. The source of this power is God himself in the form of the incarnate Word as this text makes abundantly clear.