My brethren - To wit, the three friends who had come to condole with him. He uses the language of brethren, to intimate what he had a right to expect from them. It is common in all languages to give the name brethren to friends.
Have dealt deceitfully - That is, I have been sadly disappointed. I looked for the language of condolence and compassion; for something to cheer my heart, and to uphold me in my trials - as weary and thirsty travelers look for water and are sadly disappointed when they come to the place where they expected to find it, and find the stream dried up. The simile used here is exquisitely beautiful, considered as a mere description of an actual occurrence in the deserts of Arabia. But its chief beauty consists in its exact adaptation to the case before him, and the point and pith of the reproof which it administers. “The fullness, strength, and noise of these temporary streams in winter, answer to the large professions made to Job in his prosperity by his friends. The dryness of the waters at the approach of summer, resembles the failure of their friendship in time of affliction.” Scott, as quoted by Noyes.
As a brook - That is, as a stream that is swelled by winter torrents, and that is dry in summer. Such streams abound in Arabia, and in the East generally. The torrents pour down from the hills in time of rain, or when swelled by the melting of the ice; but in summer they are dry, or their waters are lost in the sand. Even large streams are thus absorbed. The river Barrady, which waters Damascus, after passing to a short distance to the southeast of the city toward the Arabian deserts, is lost in the sand, or evaporated by the heat of the sun. The idea here is, that travelers in a caravan would approach the place where water had been found before, but would find the fountain dried up, or the stream lost in the sand; and when they looked for refreshment, they found only disappointment. In Arabia there are not many rivers. In Yemen, indeed, there are a few streams that flow the year round, and on the East the Euphrates has been claimed as belonging to Arabia. But most of the streams are winter torrents that become dry in summer, or rivulets that are swelled by heavy rains.
An illustration of the verse before us occurs in Campbell’s Travels in Africa. “In desert parts of Africa it has afforded much joy to fall in with a brook of water, especially when running in the direction of the journey, expecting it would prove a valuable companion. Perhaps before it accompanied us two miles it became invisible by sinking into the sand; but two miles farther along it would reappear and raise hopes of its continuance; but after running a few hundred yards, would sink finally into the sand, no more again to rise.” A comparison of a man who deceives and disappoints one to such a Stream is common in Arabia, and has given rise, according to Schultens, to many proverbs. Thus, they say of a treacherous friend, “I put no trust in thy torrent;” and, “O torrent, thy flowing subsides.” So the Scholiast on Moallakat says, “a pool or flood was called Gadyr, because travelers when they pass by it find it full of water, but when they return they find nothing there, and it seems to have treacherously betrayed them. So they say of a false man, that he is more deceitful than the appearance of water” - referring, perhaps, to the deceitful appearance of the mirage in the sands of the desert; see the notes at Isaiah 35:7.
And as the stream of brooks they pass away - As the valley stream - the stream that runs along in the valley, that is filled by the mountain torrent. They pass away on the return of summer, or when the rain ceases to fall, and the valley is again dry. So with the consolations of false friends. They cannot be depended on. All their professions are temporary and evanescent.