Before I go - from where "I shall not return." To the grave, to the land of shades, to
"That undiscovered country, from whose bourne
No traveler returns."
To the land of darkness - This passage is important as furnishing an illustration of what was early understood about the regions of the dead. The essential idea here is that it was a land of darkness, of total and absolute night. This idea Job presents in a great variety of forms and phrases. He amplifies it, and uses apparently all the epithets which he can command to represent the utter and entire darkness of the place. The place referred to is not the grave, but the region beyond, the abode of departed spirits, the Hades of the ancients; and the idea here is, that it is a place where not a clear ray of light ever shines. That this was a common opinion of the ancients in regard to the world of departed spirits, is well known. Virgil thus speaks of those gloomy regions:
Oii, quibusimperium est animarum, umbraeque silentes,
Et Chaos, et Phlegethon, loca nocte tacentia late,
Sit mihi fas audita loqui; slt numine vestro
Pandere res alta terra et caligine mersas.
Ibant obscuri sola sub nocte per umbram,
Perque domos Ditis vacuas, et inania regna:
Quale per incertam lunam sub luce maligna
Esther iter in silvis: ubi coelum condidit umbra
Jupiter, et rebus nox abstulit atra colorem
Aeneid vi. 259ff
A similar view of Hades was held by the Greeks. Thus, Theognis, 1007:
Ὠς μάκαρ εὐδυίμων τε και ὄλβιος, ὅστις ἄπειρος
Ἄθλων, εἰς ἥ δου δῶμα μέλαν κατέβη.
Hōs makar eudaimōn te kai olbios, hostis apeiros
Athlōn eis h' dou dōma melan katebē.
There is nowhere to be found, however, a description which for intensity and emphasis of expression surpasses this of Job.
Shadow of death - See this phrase explained in the note at Job 3:5.

I shall not return - I shall not return again from the dust to have a dwelling among men.
To the land of darkness - See the notes on Job 3:5. There are here a crowd of obscure and dislocated terms, admirably expressive of the obscurity and uncertainty of the subject. What do we know of the state of separate spirits? What do we know of the spiritual world? How do souls exist separate from their respective bodies? Of what are they capable and what is their employment? Who can answer these questions? Perhaps nothing can be said much better of the state than is here said, a land of obscurity, like darkness. The shadow of death - A place where death rules, over which he projects his shadow, intercepting every light of every kind of life. Without any order, ולא סדרים velo sedarim, having no arrangements, no distinctions of inhabitants; the poor and the rich are there, the master and his slave, the king and the beggar, their bodies in equal corruption and disgrace, their souls distinguished only by their moral character. Stripped of their flesh, they stand in their naked simplicity before God in that place.

Before I go [whence] I shall not (t) return, [even] to the land of darkness and the shadow of death;
(t) He speaks this in the person of a sinner, that is overcome with passions and with the feeling of God's judgments and therefore cannot apprehend in that state the mercies of God, and the comfort of the resurrection.

Before I go whence I shall not return,.... Before he went out of the world, the way of all flesh, to the grave, his long home, from whence there is no return to this world, and to the business and affairs of it; to a man's house, his family and his friends, to converse with them as before, there will be no return until the resurrection, which Job does not here deny, as some have thought; it was a doctrine he well understood, and strongly asserts in Job 19:26; but this must be understood in the same sense as in Job 7:9,
even to the land of darkness, and the shadow of death; which describes not the state of the damned, as some Popish interpreters, carry it; for Job had no thought nor fear of such a state; but the grave, which is called "a land", or country, it being large and spacious, and full of inhabitants; a land of "darkness", a very dark one, where the body separated from the soul is deprived of all light; where the sun, moon, and stars, are never seen; nor is there the least crevice that light can enter in at, or be seen by those that dwell in those shades, which are "the shadow of death" itself; deadly shades, thick and gross ones, the darkest shades, where death itself is, or dead men are, destitute of light and life; where no pleasure, comfort, and conversation, can be had; and therefore a land in itself most undesirable.