Albert Barnes on 1 John 5:12

He that hath the Son, hath life. Jn 5:24. John evidently designs to refer to that passage in the verse before us, and to state a principle laid down by the Saviour himself. This is the sense of all the important testimony that had ever been borne by God on the subject of salvation, that he who believes in the Lord Jesus already has the elements of eternal life in his soul, and will certainly obtain salvation. Comp. Jn 17:3.

And he that hath not the Son of God, hath not life. He that does not believe on him will not attain to eternal life. Jn 3:36; Mk 16:16.

(c) "He that" Jn 5:24