Sahih Muslim Book 26, Hadith Number 5564.

Chapter : The desirability of killing a Gecko (House Lizard).

Abu Huraira reported Allah’s Messenger (may peace be upon him) as saying: He who killed a gecko with the first stroke for him is such and such a reward, and he who killed it with a second stroke for him is such and such reward less than the first one, and he who killed it with the third stroke for him is such and such a reward less than the second one.