Revelation 1:18

Translate as Greek, "And THE LIVING ONE": connected with last sentence, Rev 1:17. and was--Greek, "and (yet) I became." alive for evermore--Greek, "living unto the ages of ages": not merely "I live," but I have life, and am the source of it to My people. "To Him belongs absolute being, as contrasted with the relative being of the creature; others may share, He only hath immortality: being in essence, not by mere participation, immortal" [THEODORET in TRENCH]. One oldest manuscript, with English Version, reads Amen." Two others, and most of the oldest versions and Fathers, omit it. His having passed through death as one of us, and now living in the infinite plenitude of life, reassures His people, since through Him death is the gate of resurrection to eternal life. have . . . keys of hell--Greek, "Hades"; Hebrew, "Sheol." "Hell" in the sense, the place of torment, answers to a different Greek word, namely, Gehenna. I can release from the unseen world of spirits and from DEATH whom I will. The oldest manuscripts read by transposition, "Death and Hades," or Hell." It is death (which came in by sin, robbing man of his immortal birthright, Rom 5:12) that peoples Hades, and therefore should stand first in order. Keys are emblems of authority, opening and shutting at will "the gates of Hades" (Psa 9:13-14; Isa 38:10; Mat 16:18).

— Jamieson-Fausset-Brown Commentary (public domain)