My root was spread out by the waters - Margin, as the Hebrew, "opened." The meaning is, that it was spread abroad or extended far, so that the moisture of the earth had free access to it; or it was like a tree planted near a stream, whose root ran down to the water. This is an image designed to denote great prosperity. In the East, such an image would be more striking than with us. Here green, large, and beautiful trees are so common as to excite little or no attention. In such a country as Arabia, however, where general desolation exists, such a tree would be a most beautiful object, and a most striking image of prosperity; compare DeWette on Psalm 1:3.
And the dew lay all night upon my branch - In the absence of rain - which seldom falls in deserts - the scanty vegetation is dependent on the dews that fall at night. Those dews are often very abundant. Volney (Travels i. 51) says, "We, who are inhabitants of humid regions, cannot well understand how a country can be productive without rain, but in Egypt, the dew which falls copiously in the night, supplies the place of rain." See, also, Shaw's Travels, p. 379. "To the same cause also (the violent heat of the day), succeeded afterward by the coldness of the night, we may attribute the plentiful dews, and those thick, offensive mists, one or other of which we had every night too sensible a proof of. The dews, particularly, (as we had the heavens only for our covering), would frequently wet us to the skin." The sense here is, as a tree standing on the verge of a river, and watered each night by copious dews, appears beautiful and flourishing, so was my condition. The Septuagint, however, renders this, "And the dew abode at night on my harvest" - καί δρόσος ἀυλισθήσεται ἐν τῷ θερισμῷ μου kai drosos aulisthēsetai en tō therismō mou. So the Chaldee - וטלא בחצדי יבית. A thought, similar to the one in this passage, occurs in a Chinese Ode, translated by Sir William Jones, in his works, vol. ii. p. 351:
Vide illius aquae rivum
Virides arundines jucunde luxuriant!
Sic est decorus virtutibus princeps noster!
"Seest thou yon stream, around whose banks
The green reeds crowd in joyous ranks?
In nutrient virtue and in grace,
Such is the Prince that rules our race."
Dr. Good

My root was spread out by the waters - A metaphor taken from a healthy tree growing beside a rivulet where there is plenty of water; which in consequence flourishes in all seasons; its leaf does not wither, nor its fruit fall off. See Psalm 1:3; Jeremiah 17:8.

My root [was] (n) spread out by the waters, and the dew lay all night upon my branch.
(n) My happiness increases.

My root was spread out by the waters,.... According to our version and others, Job here, and in the following verses, gives the reasons of his hope and confidence of his long life, and quiet and comfortable death amidst all his prosperity and happiness; which were founded upon his flourishing circumstances, and the great respect that was shown him among men; and this is the sense, if we read the words in the past tense, as we and many others do; or in the present tense, "my root is spread", &c. as others; but there are some interpreters, both Jewish and Christian (b), that render them in the future tense, here and to the end of the chapter; and so they are a continuation of Job's hope and trust, in the times of his prosperity, that things would always continue as they were with him, and much more abundantly; and indeed all is true of Job, in every sense, and all may be taken into the account; and that these words, and the following, as they describe what had been, and at the then present time, when he concluded the above in his mind, was his case, so they may also declare what he believed would be always his case to the end of his days. Here he compares himself to a tree well rooted and happily situated by plenty of water, and which may be expressive both of his temporal and spiritual prosperity: his outward prosperity seemed to him to have been well settled and established, being like a tree that had taken root, and was like to continue, being watered with the favour and blessing of God, which maketh rich; and as to his spiritual estate, he was like a tree planted by a river of water, to which good men are often compared in Scripture, Psalm 1:3; they are in general called trees of righteousness, and are sometimes likened to particular trees, as to olives, cedars, and palm trees; and some think, as Pineda, that it is to the latter Job here has respect; the last clause of Job 29:18 being in the Latin Vulgate version so rendered as to countenance this sense; and it may be observed that this tree having thick long leaves, and fruit full of juice, and its wood spongy, requires much water; and, as Pliny (c) says, delights in watery places; nor is it content with rain, but is better satisfied with waters flowing about it; hence it is often found necessary to dig about it, and lay its roots open, that the waters may more easily come at them, and flow about them (d) and so the words here in the original text are, "my root" was, is, or shall be "open to the waters" (e): good men, as they are rooted in the love of God, and in the person of Christ, so they have, as Job had, the root of the matter in them, the truth of grace, or a principle of grace; which is watered, and kept alive and flourishing, by the love and favour of God shed abroad in the heart; by fresh supplies of grace out of the fulness of Christ, who is the fountain of gardens, and well of living waters; and by the means of grace, the word and ordinances, the still waters to which saints are led, and by which they are made to lie down, and where they are watered, refreshed, and comforted:
and the dew lay all night upon my branch; so that the water being at his root below, and the dew on his branch above, he must be in a fruitful and flourishing condition: the dew is a great blessing to the earth, to trees, herbs, and plants, and the cause of great fertility; and this may respect Job's temporal happiness, in the health and prosperity of his children, who were to him what branches are to a tree; and in the affluence of worldly good things, with which through the blessing of God, as dew upon him, he abounded; and may also have regard to his spiritual affairs: believers in Christ are branches in him, as Job was one; and the dew of divine grace and favour lies upon them continually, even in the darkest seasons; which revives and refreshes their souls, and makes them fruitful in the exercise of grace, and performance of good works; see Proverbs 19:12; the dew falls in the night, and the sooner it fails the longer it lies, and is most useful: some render the words "upon my harvest", or "mowing" (f); the dew is of great use in harvest time; mowers and reapers choose the morning to work in, when the stalks are moistened by the dew; and which is of use to keep the ears of corn from shedding by swelling the fibres, and so retaining the grains in their proper places (g); see Isaiah 18:4.
(b) Jarchi, Ben Gerson, Bar Tzemach, Schmidt, Schultens. (c) Nat. Hist. l. 13. 4. (d) Palladius apud Scheuchzer, ut supra (Physic. Sacr. l. vol. 4.), p. 759. (e) "aperta ad aquas", Montanus, Bolducius, Mercerus, Cocceius, Schmidt, Michaelis, Schultens. (f) "in messe mea", Montanus, Tigurine version; "in segete mea", Cocceius; so the Targum. (g) Vid. Scheuchzer, ut supra. (Physic. Sacr. l. vol. 4. p. 759.)

Literally, "opened to the waters." Opposed to Job 18:16. Vigorous health.