Albert Barnes Commentary Job 21:20

"Let his own eyes see his destruction, And let him drink of the wrath of the Almighty." — Job 21:20 (ASV)

His eyes shall see his destruction - That is, his own eyes will see his destruction, or the calamities that will come upon him. That is, “You maintain that, or this is the position which you defend.” Job intends to address this and to show that it is not always so.

And he shall drink of the wrath of the Almighty - Wrath is often represented as a cup which the wicked are compelled to drink. See the notes (Isaiah 51:17).