That they were graven with {p} an iron pen and lead in the rock for ever!

(p) He protests that despite his sore passions his religion is perfect and that he in not a blasphemer as they judged him.

Wesley's Notes

19:24 Lead - Anciently they used to grave the letters in a stone with an iron tool, and then to fill up the cuts with lead, that the words might be more plainly seen.

Jamieson-Fausset-Brown Bible Commentary

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.

Matthew Henry's Concise Commentary

19:23-29 The Spirit of God, at this time, seems to have powerfully wrought on the mind of Job. Here he witnessed a good confession; declared the soundness of his faith, and the assurance of his hope. Here is much of Christ and heaven; and he that said such things are these, declared plainly that he sought the better country, that is, the heavenly. Job was taught of God to believe in a living Redeemer; to look for the resurrection of the dead, and the life of the world to come; he comforted himself with the expectation of these. Job was assured, that this Redeemer of sinners from the yoke of Satan and the condemnation of sin, was his Redeemer, and expected salvation through him; and that he was a living Redeemer, though not yet come in the flesh; and that at the last day he would appear as the Judge of the world, to raise the dead, and complete the redemption of his people. With what pleasure holy Job enlarges upon this! May these faithful sayings be engraved by the Holy Spirit upon our hearts. We are all concerned to see that the root of the matter be in us. A living, quickening, commanding principle of grace in the heart, is the root of the matter; as necessary to our religion as the root of the tree, to which it owes both its fixedness and its fruitfulness. Job and his friends differed concerning the methods of Providence, but they agreed in the root of the matter, the belief of another world.