Because it shut not up - That is, because the accursed day and night did not do it. Aben Ezra supposes that God is meant here, and that the complaint of Job is that he did not close his mother's womb. But the more natural interpretation is to refer it to the Νυχθήμεροι Nuchthēmeroi - the night and the day which he had been cursing, on which he was born. Throughout the description the day and the night are personified, and are spoken of as active in introducing him into the world. He here curses them because they did not wholly prevent his birth.
Nor hid sorrow from mine eyes - By preventing my being born. The meaning is, that he would not have known sorrow if he had then died.

Because it shut not up the doors - Here is the reason why he curses the day and the night in which he was conceived and born; because, had he never been brought into existence, he would never have seen trouble. It seems, however, very harsh that he should have wished the destruction of his mother, in order that his birth might have been prevented; and I rather think Job's execration did not extend thus far. The Targum understands the passage as speaking of the umbilical cord, by which the fetus is nourished in its mother's womb: had this been shut up, there must have been a miscarriage, or he must have been dead born; and thus sorrow would have been hidden from his eyes. This seeming gloss is much nearer the letter and spirit of the Hebrew than is generally imagined. I shall quote the words: כי לא סגר דלתי בטני ki lo sagar dalthey bitni, because it did not shut up the doors of my belly. This is much more consistent with the feelings of humanity, than to wish his mother's womb to have been his grave.

Because it shut not up the doors of my mother's womb,.... Or "of my belly" (m), or "womb"; which Aben Ezra interprets of the navel, by which the infant receives its food and nourishment before it is born, and which, if closed, he must have died in embryo; but rather it is to be understood of his mother's womb, called his, because he was conceived and bore in it, and was brought forth from it; and the sense is, that he complains of the night, either that it did not close his mother's womb, and hinder the conception of him, as Gersom, Sephorno, Bar Tzemach, and others, and is the usual sense of the phrase of closing the womb, and which is commonly ascribed to God, Genesis 20:17 1-Samuel 1:5; which Job here attributes to the night, purposely avoiding to make mention of the name of God, that he might not seem to complain of him, or directly point at him; or else the blame laid on that night is, that it did not so shut up the doors of his mother's womb, that he might not have come out from thence into the world, wishing that had been his grave, and his mother always big with him, as Jarchi, and which sense is favoured by Jeremiah 20:17; a wish cruel to his mother, as well as unnatural to himself:
nor hid sorrow from mine eyes; which it would have done, had it done that which is complained of it did not; had it he could not have perceived it experimentally, endured the sorrows and afflictions he did from the Chaldeans and Sabeans, from Satan, his wife, and friends; and had never known the trouble of loss of substance, children, and health, and felt those pains of body and anguish of mind he did; these are the reasons of his cursing the day of his birth, and the night of his conception.
(m) "ventris mei", Mercerus, Piscator, Schmidt, Schuitens, Michaelis; "uteri mei", Pagninus, Montanus, Junius & Tremellius, Cocceius.

10 Because it did not close the doors of my mother's womb,
Nor hid sorrow from my eyes.
11 Why did I not die from the womb,
Come forth from the womb and expire?
12 Why have the knees welcomed me?
And why the breasts, that I should suck?
The whole strophe contains strong reason for his cursing the night of his conception or birth. It should rather have closed (i.e., make the womb barren, to be explained according to 1-Samuel 1:5; Genesis 16:2) the doors of his womb (i.e., the womb that conceived concepit him), and so have withdrawn the sorrow he now experiences from his unborn eyes (on the extended force of the negative, vid., Ges. 152, 3). Then why, i.e., to what purpose worth the labour, is he then conceived and born? The four questions, Job 3:11., form a climax: he follows the course of his life from its commencement in embryo (מרהם, to be explained according to Jeremiah 20:17, and Job 10:18, where, however, it is מן local, not as here, temporal) to the birth, and from the joy of his father who took the new-born child upon his knees (comp. Genesis 50:23) to the first development of the infant, and he curses this growing life in its four phases (Arnh., Schlottm.). Observe the consecutio temp. The fut. אמוּת has the signification moriebar, because taken from the thought of the first period of his conception and birth; so also ואגוע, governed by the preceding perf., the signification et exspirabam (Ges. 127, 4, c). Just so אינק, but modal, ut sugerem ea.

It - The night or the day: to which those things are ascribed which were done by others in them, as is frequent in poetical writings. Womb - That it might never have brought me forth. Nor hid - Because it did not keep me from entering into this miserable life, and seeing, or experiencing, these bitter sorrows.