John 1:12-13 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: Which were born, not of blood, nor of the will of the flesh, nor of the will of man, but of God.

Verses 10 and 11 teach that although He created the world, the world outside of Israel, did not know of Him. Even still, although they were looking for a Messiah, even His own did not recieve Him as being the Son of God.

Here John teaches that to each one who did accept His position as the Christ, and especially to those who put their trust and faith in His authority, He extended the liberty of becoming children of God. To clarify, this is referring to the free will choice made by the person. Those who accepted Him as being the Son of God had all that was needed to convert and become a new creature, living and walking after the Spirit. This is especially true concerning those believers who did just that. Having already been adopted by God and made children by regeneration, they have now become children of God from their own perspective, knowing God as their Father. The Greek word translated "sons" is "the name transferred to that intimate and reciprocal relationship formed between men by the bonds of love, friendship, trust, just as between parents and children".

These were made children, not by the offering of sacrifice, nor by the inclination of the human nature, nor by the choice of moral excellence, but of God.

This means that God had written His laws in their heart. In Thayers’ Lexicon, the following quote is found, "If one teaches the son of his neighbor the law, the Scripture reckons this the same as though he had begotten him". As explained in Ephesians 1:13, when a person trusts in the gospel and believes in Christ, the Holy Spirit is given and thus the prophecy is fulfilled: "After those days, saith the LORD, I will put my law in their inward parts, and write it in their hearts; and will be their God, and they shall be my people".