(33) باب إِذَا شَرِبَ الْكَلْبُ فِي إِنَاءِ أَحَدِكُمْ فَلْيَغْسِلْهُ سَبْعًا
Narrated Abu Huraira:
The Prophet (ﷺ) said, "A man saw a dog eating mud from (the severity of) thirst. So, that man took a shoe (and filled it) with water and kept on pouring the water for the dog till it quenched its thirst. So Allahapproved of his deed and made him to enter Paradise."
Reference: Sahih al-Bukhari 173
In-book reference: Book 4, Hadith 39
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 1, Book 4, Hadith 174