I John 5:9-11

If we receive the witness of men, the witness of God is greater; for this is the witness of God which He has testified of His Son. He who believes in the Son of God has the witness in himself; he who does not believe God has made Him a liar, because he has not believed the testimony that God has given of His Son. And this is the testimony: that God has given us eternal life, and this life is in His Son.