Jamieson, Fausset and Brown on Hebrews 2:15

15. fear of death--even before they had experienced its actual power.

all their lifetime--Such a life can hardly be called life.

subject to bondage--literally, "subjects of bondage"; not merely liable to it, but enthralled in it (compare Ro 8:15; Ga 5:1). Contrast with this bondage, the glory of the "sons" (He 2:10). "Bondage" is defined by Aristotle, "The living not as one chooses"; "liberty," "the living as one chooses." Christ by delivering us from the curse of God against our sin, has taken from death all that made it formidable. Death, viewed apart from Christ, can only fill with horror, if the sinner dares to think.