Every one who believes that Jesus is the Christ is a child of God, and every one who loves the parent loves the child. By this we know that we love the children of God, when we love God and obey his commandments. For this is the love of God, that we keep his commandments. And his commandments are not burdensome. For whatever is born of God overcomes the world; and this is the victory that overcomes the world, our faith. Who is it that overcomes the world but he who believes that Jesus is the Son of God?
This is he who came by water and blood, Jesus Christ, not with the water only but with the water and the blood. And the Spirit is the witness, because the Spirit is the truth. There are three witnesses, the Spirit, the water, and the blood; and these three agree. If we receive the testimony of men, the testimony of God is greater; for this is the testimony of God that he has borne witness to his Son. He who believes in the Son of God has the testimony in himself. He who does not believe God has made him a liar, because he has not believed in the testimony that God has borne to his Son. And this is the testimony, that God gave us eternal life, and this life is in his Son. He who has the Son has life; he who has not the Son of God has not life.
–1 John 5:1-12