When a physician consulted the Prophet ﷺ about putting frogs in medicine, he forbade him to kill them.  

أَنَّ طَبِيبًا سَأَلَ النَّبِيَّ ﷺ عَنْ ضِفْدَعٍ يَجْعَلُهَا فِي دَوَاءٍ فَنَهَاهُ النَّبِيُّ ﷺ عَنْ قَتْلِهَا