1 John 5:1, 5, 10-13, 20

Whosoever believeth that Jesus is the Christ is begotten of God: and whosoever loveth him that begat loveth him also that is begotten of him.

And who is he that overcometh the world, but he that believeth that Jesus is the Son of God?

He that believeth on the Son of God hath the witness in him: he that believeth not God hath made him a liar; because he hath not believed in the witness that God hath borne concerning his Son. And the witness is this, that God gave unto us eternal life, and this life is in his Son. He that hath the Son hath the life; he that hath not the Son of God hath not the life. These things have I written unto you, that ye may know that ye have eternal life, even unto you that believe on the name of the Son of God.

And we know that the Son of God is come, and hath given us an understanding, that we know him that is true, and we are in him that is true, even in his Son Jesus Christ. This is the true God, and eternal life.