They spend their days in wealth - Margin, or, “mirth.” Literally, “they wear out their days in good” - בטוב baṭôb. Vulgate “in bonis.” Septuagint, ἐν ἀγαθοῖς en agathois - “in good things;” in the enjoyment of good. They are not oppressed with the evils of poverty and want, but they have abundance of “the good things” of life.
And in a moment go down to the grave - Hebrew to שׁאול she'ôl - but here meaning evidently the grave. The idea is, that when they die they are not afflicted with lingering disease, and great bodily pain, but having lived to an old age in the midst of comforts, they drop off suddenly and quietly, and sleep in the grave. God gives them prosperity while they live, and when they come to die he does not come forth with the severe expressions of his displeasure, and oppress them with long and lingering sickness. The author of Psalms 73 had a view of the death of the wicked remarkably similar to this, when he said,
For I was envious at the foolish,
When I saw the prosperity of the wicked.
For there are no bands in their death,
But their strength is firm. Psalms 73:3-4.
All that Job says here is predicated on the supposition that such a sudden removal is preferable to death accompanied with long and lingering illness. The idea is, that it is in itself “desirable” to live in tranquility; to reach an honorable old age surrounded by children and friends, and then quietly and suddenly to drop into the grave without being a burden to friends. The wicked, he says, often live such a life, and he infers, therefore, that it is not a fact that God deals with people according to their character in this life, and that it is not right to draw an inference respecting their moral character from his dealings with them in this world. There are instances enough occurring in every age like those supposed here by Job, to justify the conclusion which he draws.