John Trapp on Job 15:31

Verſe 31. Let not him that it deceived, truſt in vanity.] Let it ſuffice him that he hath been once already deceived by the uncertainty of riches, which were never true to thoſe which truſted them, nor never will be, 1 Tim. 6.17. As Charendas was wont to ſay of going to ſea, (and another of going to Law) That he wondred not at thoſe that go once, but at thoſe who go a ſecond time. So may we at thoſe that having found the deceitfulneſſe of ſin, and the inſtability of Creature-comforts, that they ſhould again be drawn in and deceived. This folly Eliphaz here forewarneth Job of, and would not have him twice ſtumble at the ſame ſtone, but deliver his ſoul, (if ever God ſhould reſtore him again) and ſay, Is there not a lye in my right hand? Why feed I upon aſhes? &c. Iſai. 44.20.

For vanity ſhalt be his recompence.] i.e. Poverty and miſery ſhall be his portion, as ſhame ſhall be the portion of fools, Prov. 3.35. As he hath ſowed the wind, ſo he ſhall reap the whirlewind, whereof he is likely to have a great catch, Hoſ. 8.7. See the Note there.