“He that believeth on the Son of God hath the witness in himself: he that believeth not God hath made him a liar; because he believeth not the record that God gave of his Son.”
King James Version (KJV)
5:10 He that believeth on the Son of God hath the testimony - The dear evidence of this, in himself: he that believeth not God, in this, hath made him a liar; because he supposes that to be false which God has expressly testified.
1Jo 5:10 He that believeth on the Son of God hath the witness in himself. He hath the witness in his changed heart and life. He that believeth not God hath made him a liar. He makes God a liar by rejecting the witness God gives to the Son.