Jamieson, Fausset and Brown on Job 6:15

15. Those whom I regarded as "my brethren," from whom I looked for faithfulness in my adversity, have disappointed me, as the streams failing from drought--wadies of Arabia, filled in the winter, but dry in the summer, which disappoint the caravans expecting to find water there. The fulness and noise of these temporary streams answer to the past large and loud professions of my friends; their dryness in summer, to the failure of the friendship when needed. The Arab proverb says of a treacherous friend, "I trust not in thy torrent" (Is 58:11, Margin).

stream of brooks--rather, "the brook in the ravines which passes away." It has no perpetual spring of water to renew it (unlike "the fountain of living waters," Jr 2:13; Is 33:16, at the end); and thus it passes away as rapidly as it arose.