Musnad Ahmad 512:1

Ya'la narrated to us, Muhammad—meaning Ibn Ishaq—informed us, from al-Zuhri, from 'Abd al-Rahman ibn Malik ibn Ju'sham, from his father, from his uncle Suraqah ibn Ju'sham, who said: I asked the Messenger of Allah, may Allah bless him and grant him peace, about a stray camel that comes to my watering troughs: "Do I have a reward if I give it water?" He said: "Yes, in every living creature with a burning liver [i.e., a thirsty living being], there is a reward."