For what does he care about his household after him, when the number of his months has run out?
Job had largely described the prosperity of wicked people; now, in these verses, I. He opposes this to what his friends had maintained concerning their certain ruin in this life. "Tell me how often do you see the candle of the wicked put out? Do you not as often see it burnt down to the socket, until it goes out of itself? Job 21:17.
Commenting on Job 21:17-26
Shall any teach God knowledge?.... Who is a God of knowledge, and knows all things, that teaches men knowledge; will any one take upon him to teach him the path of judgment, and the way of understanding, how he shall govern the world, and dispose of men and things in it? see Isa 40:13.
The argument of the friends, in proof of Job 21:20, What pleasure can he have from his house (children) when he is dead--("after him," Ecc 3:22). when the number, &c.--Or, rather, "What hath he to do with his children?" &c. (so the Hebrew in Ecc 3:1; Ecc 8:6). It is therefore necessary that "his eyes should see his and their destruction" (see Job 14:21).