hath given - Greek, aorist: “gave” once for all. Not only “promised” it.
life is in his Son - essentially (Joh 1:4; Joh 11:25; Joh 14:6); bodily (Col 2:9); operatively (2Ti 1:10) [Lange in Alford]. It is in the second Adam, the Son of God, that this life is secured to us, which, if left to depend on us, we should lose, like the first Adam.