Albert Barnes Commentary Job 12:20

"He removeth the speech of the trusty, And taketh away the understanding of the elders." — Job 12:20 (ASV)

He removes away the speech of the trusty - Margin, “lip of the faithful.” “He takes away the lip,” that is, he takes away the power of giving safe counsel or good advice. The “trusty” or “faithful” here refer to those of age and experience, and on whose counsel people are accustomed to rely. The meaning here is that their most sagacious anticipations are disappointed, and their wisest schemes are foiled. They fail in their calculations of the course of events, and the arrangements of Providence are such that they could not anticipate what would occur.

The understanding of the aged - To whom the young were accustomed to look up with deference and respect. The meaning here is that those who were accustomed to give wise and sound advice, if left by God, give vain and foolish counsels.