Abu Dawud
General Behavior
Book Number: 036 / Hadith Number: 5243
Narated By AbuHurayrah : The Prophet (pbuh) said: If anyone kills a gecko with the first blow, such and such number of good deeds will be recorded for him, if he kills it with the second blow, such and such number of good deeds will be recorded for him less than the former; and if he kills it with the third blow, such and such number of good deeds will be recorded for him, less than the former.