John 1:12-13

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.

To receive Christ, a man must be born of God. It is the simplest thing in all the world, one would think, to open the door of the heart, and let him in; but no man lets Christ into his heart till first God has made him to be born again, born from above.