Kommentar zu Ijow 2:6

but preserve his life that it does not go out. From here the Sages said, “The Adversary’s pain was greater than Job’s. This is analogous to one saying to his friend, ‘Break this barrel but preserve its wine.’”

God agrees to this second test adding the rider that Job was not actually to die. The Talmudic Sages observed, in irony, that Satan's frustration at this rider was even greater than all the pain suffered by Job. It was as though he had been told to 'break the cask but to save the wine' (TB Baba Batra 16a).