Commentary for Pesachim 111:20

AND HE HID THE BOOK OF REMEDIES. As it is written (II Kings 20:3; Isa. 38:3), "I have done what is pleasing (and righteous) to You." And we said in B'rachot that he hid the Book of Remedies because their minds were not subdued by the illness; instead, they would be healed instantly.