John 8:51

The central purpose of Jesus’ mission was not glory for Himself but glory for His Father through salvation for humankind. Jesus’ introduction of this strong statement shows its vital importance. Keeping Jesus’ word is synonymous with believing on Him (cf. John 5:24; John 8:24). The death in view is eternal death (cf. John 11:25).

"The assurance relates to life which physical death cannot extinguish, and so to the death of the spirit; the believer receives eternal life, i.e., the life of the kingdom of God, over which death has no power and which is destined for resurrection." [Note: Beasley-Murray, p. 137.]