Jami` at-Tirmidhi 1482
جامع الترمذي#1482SahihNarrated Abu Hurairah:That the Messenger of Allah (ﷺ) said: "Whoever kills a gecko in one strike, he has such and such reward, and if he kills it on the second strike, he will have such and such reward, and if he kills it on the third strike, then he has such and such reward
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Ahmad Muhammad ShakirSahih
Al-AlbaniSahih
Bashar Awad MaaroufHasan Sahih
Zubair Ali ZaiSahih - Bukhari And Muslim
In-book reference: 18:23