Jamieson, Fausset and Brown on Job 29:24

24. When I relaxed from my wonted gravity (a virtue much esteemed in the East) and smiled, they could hardly credit it; and yet, notwithstanding my condescension, they did not cast aside reverence for my gravity. But the parallelism is better in Umbreit's translation, "I smiled kindly on those who trusted not," that is, in times of danger I cheered those in despondency. And they could not cast down (by their despondency) my serenity of countenance (flowing from trust in God) (Pr 16:15; Psa 104:15). The opposite phrase (Ge 4:5, 6). "Gravity" cannot well be meant by "light of countenance."