To see death, in this text, signifieth to die, but in an apparently differing sense from what it is taken in Luke 2:26, where it is to be understood of a natural death; of which it cannot be understood here, for the holiest men shall die: the body is dead (that is, in dying) because of sin; or, shall die because of sin, Romans 8:10. It must therefore be understood of death eternal; and in that sense the proposition is certainly true, That a holy man that keepeth the sayings of Christ shall not see death, that is, shall have eternal life; which is no more than what we have often before met with, viz. the promise of life eternal to faith and holiness.
Related Commentaries of John 8:51
John 8:51
51 Verily, verily, I say unto you, If a man keep my saying, he shall never see death.