Jamieson, Fausset and Brown on Job 19:24

24. pen--graver.

lead--poured into the engraven characters, to make them better seen [Umbreit]. Not on leaden plates; for it was "in the rock" that they were engraved. Perhaps it was the hammer that was of "lead," as sculptors find more delicate incisions are made by it, than by a harder hammer. FOSTER (One Primeval Language) has shown that the inscriptions on the rocks in Wady-Mokatta, along Israel's route through the desert, record the journeys of that people, as Cosmas Indicopleustes asserted, A.D. 535.

for ever--as long as the rock lasts.