The Messenger of Allah ﷺ said, "Whoever shows mercy, even to an animal being slaughtered, Allah will show mercy to him on the Day of Resurrection."
قال رسول الله ﷺ: من رحم ولو ذبيحة، رحمه الله يوم القيامة.
No references are available.
Bukhari narrated it in Al-Adab (381), from Mahmud, who said, our teacher Yazid told us, saying, Walid bin Jameel Kindi informed us, from Qasim bin Abdul-Rahman, from Abu Umama, and he related it.Its chain is hasan because of Walid bin Jameel, about whom there is disagreement, except that his hadith is hasan so long as there is no nakarah (irregularity) in it, for he narrated some objectionable hadiths from Qasim.His saying, "even if it is a slaughtered animal, if he shows mercy" means that he slaughters it with a sharp knife and gives the slaughtered animal ease.