Jamieson, Fausset and Brown on Job 12:5

5. Rather, "a torch" (lamp) is an object of contempt in the thoughts of him who rests securely (is at ease), though it was prepared for the falterings of the feet [Umbreit] (Pr 25:19). "Thoughts" and "feet" are in contrast; also rests "securely," and "falterings." The wanderer, arrived at his night-quarters, contemptuously throws aside the torch which had guided his uncertain steps through the darkness. As the torch is to the wanderer, so Job to his friends. Once they gladly used his aid in their need; now they in prosperity mock him in his need.