Whoever believes in the Son of God has this testimony within him; whoever does not believe God has made Him out to be a liar, because he has not believed in the testimony that God has given about His Son.
KJV
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.
ASV
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.