Matthew Poole and continuators on Job 7:3

3. So am I made to possess months of vanity , and wearisom nights are appointed to me.

This so respects not so much the desire and expectation of an hired Servant, which is expressed, v. 2. as the ground and reason of it, which is plainly implied there, to wit, his hard toil and service, which makes him thirst after rest.

God by his soveraign Power and Providence hath given me thus as my lot and inheritance.

So he calls them rather than daies, to note either the irksomness and tediousness of his affliction, whereby every day seemed a month to him, or their length and continuance, which, as some infer from hence, had now been upon him some months

Empty and unsatisfying, or false and deceitful, not giving me that ease and rest, which they promised me, and I expected.

He mentions nights, because that is the saddest time for sick and miserable persons; the darkness and solitude of the night being of themselves uncomfortable, and giving them more opportunity for solemn and sorrowful thoughts and reflections upon their own miseries.