The bright shining of a candle (ὁ λύχνος τῇ ἀστραπῇ)
More correctly, as Rev., the lamp with its bright shining. Ἀστραπή means lightning: see Luk 10:18; and that is the usual meaning in classical Greek, though it occurs, rarely, of the light of a lamp. It is used here to emphasize the idea of moral illumination.