There is death in the pot, i.e. some deadly thing; which they gathered from its excessive bitterness, by which possibly some of them might discern what it was.
Related Commentaries of 2 Kings 4:40
2 Kings 4:40
40 So they poured out for the men to eat. And it came to pass, as they were eating of the pottage, that they cried out, and said, O thou man of God, there is death in the pot. And they could not eat thereof.