Then thou scarest me - This is an address to God. He regarded him as the source of his sorrows, and he expresses his sense of this in language indeed very beautiful, but far from reverence.
With dreams - see Job 7:4. A similar expression occurs in Ovid:
Ut puto, cam requies medicinaque publica curae,
Somnus adest, soliris nox venit orba malis,
Somnia me terrent. veros imitantia casus,
Et vigilant sensus in mea damna mei.
Do Ponto, Lib. i. Eleg. 2.
And terrifiest me through visions - See the notes at Job 4:13. This refers to the visions of the fancy, or to frightful appearances in the night. The belief of such night-visions was common in the early ages, and Job regarded them as under the direction of God, and as being designed to alarm him.

Thou sparest me with dreams - There is no doubt that Satan was permitted to haunt his imagination with dreadful dreams and terrific appearances; so that, as soon as he fell asleep, he was suddenly roused and alarmed by those appalling images. He needed rest by sleep, but was afraid to close his eyes because of the horrid images which were presented to his imagination. Could there be a state more deplorable than this?

Then thou scarest me (i) with dreams, and terrifiest me through visions:
(i) So that I can have no rest, night or day.

Then thou scarest me with dreams,.... Not with dreams and visions being told him, as were by Eliphaz, Job 4:13; but with dreams he himself dreamed; and which might arise from the force of his distemper, and the pain of his body, whereby his sleep was broken, his imagination disturbed, and his fancy roving, which led him to objects as seemed to him very terrible and dreadful; or from a melancholy disposition his afflictions had brought upon him; and hence in his dreams he had dismal apprehensions of things very distressing and terrifying; or from Satan, in whose hands he was, and who was permitted to distress and disturb him at such seasons; all which he ascribes to God, because he suffered it so to be: and now these dreams not only hindered sound sleep, and getting that ease and refreshment he hoped for from thence, but even they were frightful and scaring to him, so that instead of being the better for his bed and his couch, he was the worse; these dreams added to his afflictions, and in them he suffered much, as Pilate's wife is said to do, Matthew 27:19,
and terrifiest me through visions; spectres, apparitions, and such like things, being presented to his fancy, while sleeping and dreaming, which filled him with terror, and sorely distressed him, so that he could receive no benefit hereby, but rather was more fatigued and weakened.

The frightful dreams resulting from elephantiasis he attributes to God; the common belief assigned all night visions to God.