Albert Barnes Commentary Job 37:20

"Shall it be told him that I would speak? Or should a man wish that he were swallowed up?" — Job 37:20 (ASV)

Shall it be told him that I speak? – This is still the language of profound awe and reverence, as if he would not want it even suggested to God that he had presumed to say anything about Him, or with a view to explain the reason for His actions.

If a man speak – that is, if he attempts to speak with God, to argue a case with Him, to contend with Him in debate, or to oppose Him. Elihu had intended to reprove Job for the bold and presumptuous manner in which he had spoken of God, and for his wish to enter into a debate with Him in order to vindicate his cause. He now says that if anyone should attempt this, God had power at once to destroy him, and that such an attempt would be perilous to his life. But other interpretations have been proposed, which may be seen in Rosenmuller, Umbreit, and Lee.

Surely he shall be swallowed up – destroyed for his presumption and rashness in thus contending with the Almighty. Elihu says that for this reason he would not dare to speak with God. He would fear that God would come forth in His anger and destroy him. How deeply man by nature instinctively feels, when he has any proper understanding of the majesty of God, that he needs a Mediator!