a physician made mention of the use of frogs in a remedy in the presence of the Messenger of Allah and the Messengher of Allah forbade killing them. (sahih)  

أَنَّ طَبِيبًا ذَكَرَ ضِفْدَعًا فِي دَوَاءٍ عِنْدَ رَسُولِ اللَّهِ ﷺ فَنَهَى رَسُولُ اللَّهِ ﷺ عَنْ قَتْلِهِ