Mishkat al-Masabih 20 Game and Animals Which May Be Slaughtered كتاب الصيد والذبائح 57

وَعَنْ أَبِي هُرَيْرَةَ أَنَّ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ قَالَ: «مَنْ قَتَلَ وَزَغًا فِي أولَّ ضَرْبَة كتبت لَهُ مِائَةُ حَسَنَةٍ وَفِي الثَّانِيَةِ دُونَ ذَلِكَ وَفِي الثَّالِثَة دون ذَلِك» . رَوَاهُ مُسلم

Abu Huraira reported God’s messenger as saying, “If anyone kills a gecko with the first blow a hundred good deeds will be recorded for him, less if he kills it at the second and less still if he kills it at the third.” Muslim transmitted it.