Origen

(tom. xx. s. 31.) We must understand Him, as it were, to say, If a man keep My light, he shall not see darkness for ever; for ever being taken as common to both clauses, as if the sentence were, If a man keep My saying for ever, He shall not see death for ever: meaning that a man does not see death, so long as he keeps Christ’s word. But when a man, by becoming sluggish in the observance of His words, and negligent in the keeping of his own heart, ceases to keep them, he then sees death; he brings it upon himself. Thus taught then by our Saviour, to the prophet who asks, What man is he that liveth, and shall not see death? (Ps. 88) we are able to answer, He who keepeth Christ’s word.