Albert Barnes Commentary Job 42:3

"Who is this that hideth counsel without knowledge? Therefore have I uttered that which I understood not, Things too wonderful for me, which I knew not." — Job 42:3 (ASV)

Who is he that hides counsel without knowledge? - This is repeated from (Job 38:2). As used there, these are the words of the Almighty, uttered as a reproof of Job for the manner in which he had undertaken to explain the dealings of God; see the notes at that verse. As repeated here by Job, they are an acknowledgment of the truth of what is there implied, that he had been guilty of hiding counsel in this manner, and the repetition here is a part of his confession. He acknowledges that he had entertained and expressed such views of God as were in fact clothing the whole subject in darkness instead of explaining it. The meaning is, "Who indeed is it, as you said, that undertakes to judge great and profound purposes without knowledge? I am that presumptuous man? Ilgen."

Therefore have I uttered that I understood not - I have pronounced an opinion on subjects altogether too profound for my comprehension. This is the language of true humility and penitence, and shows that Job had at heart a profound veneration for God, however much he had been led away by the severity of his sufferings to give vent to improper expressions. It is not uncommon for even good people to be brought to see that they have spoken presumptuously of God, and have engaged in discussions and ventured to pronounce opinions on matters pertaining to the divine administration that were wholly beyond their comprehension.