A man came to the Messenger of Allah ﷺ and said, "I draw water into my trough, and when I have filled it for my own livestock, another person's camel comes to me, so I give it water to drink. Is there any reward for me in that?"The Messenger of Allah ﷺ replied, "In every living creature with a thirsty liver there is a reward."
أن رجلا جاء إلى رسول الله ﷺ فقال: إني أنزع في حوضي حتى إذا ملأته لأهلي، ورد علي البعير لغيري فسقيته، فهل لي في ذلك من أجر؟ فقال رسول الله ﷺ: في كل ذات كبد حرى أجر.
Ahmad (7075) reported it from Harun bin Maruf, who said, Abdullah bin Wahb told us, Usama informed me, that Amr bin Shuayb told him, from his father, from his grandfather, and he related it.Its chain is hasan because of Usama, who is Ibn Zayd al-Laythi, and his source Amr bin Shuayb, for both of them make the hadith hasan.