Narrated from Sayyiduna Abdur Rahman bin Uthman (may Allah be pleased with him) that a physician mentioned to the Messenger of Allah (peace and blessings be upon him) a medicine in which he used to mix frog, but the Prophet (peace and blessings be upon him) forbade killing the frog.
Benefits: … The legal ruling regarding the frog is that it is forbidden (haram), because even in a situation of necessity, the Messenger of Allah (sallallahu alayhi wa sallam) did not permit its use. The fact that the Prophet (sallallahu alayhi wa sallam) did not grant permission is itself evidence of its prohibition. Although the frog is an aquatic animal, it can also live outside of water, and in fact, it roams outside for long periods. Therefore, it cannot be given the same ruling as aquatic animals.