Albert Barnes Commentary Job 31:40

"Let thistles grow instead of wheat, And cockle instead of barley. The words of Job are ended." — Job 31:40 (ASV)

Let thistles grow; - (Genesis 3:18). Thistles are valueless; and Job is so confident of his complete innocence regarding this that he says he would be willing, if he were guilty, to have his whole land overrun with noxious weeds.

And cockle - Cockle is a well-known herb that gets into wheat or other grain. It has a bluish flower, and small black seed, and is injurious because it tends to discolor the flour. However, it is by no means certain that this is intended here. The margin says, "noxious weeds."

The Hebrew word באשׁה (bo'shâh) is from באשׁ (bâ'ash)—meaning “to have a bad smell, to stink”—and was given to the weed referred to here on that account . The cockle, however, has no unpleasant odor, and the word here probably means noxious weeds.

So it is rendered by Herder and by Noyes. The Septuagint has βάτος (batos)—bramble; the Vulgate, spina, thorn; Professor Lee, prunus sylvestris, “a bramble resembling the hawthorn;” Schultens, labrusca, wild vine.

The words of Job are ended - That is, in the present speech or argument; his discussions with his friends are closed. He spoke afterwards, as recorded in the subsequent chapters, but not in controversy with them. He had vindicated his character, sustained his positions, and they had nothing to reply. The remainder of the book is occupied mainly with the speech of Elihu and with the solemn and sublime address which God himself makes.