Sahih Adab al-Mufrad

It is narrated from Sayyiduna Abu Hurairah (may Allah be pleased with him) that the Prophet (peace and blessings of Allah be upon him) said: "A man was walking along the road when he felt extremely thirsty. He found a well, so he went down into it and drank water. When he came out, he saw a dog panting and licking the wet earth out of thirst. The man said, 'This dog is suffering from thirst just as I was.' So he went down into the well again, filled his shoe with water, held it in his mouth, and climbed up, then gave the dog water to drink. Allah appreciated this deed of his and forgave him." The people asked, "O Messenger of Allah! Is there a reward for us in (doing good to) animals as well?" He replied, "There is a reward for (doing good to) every living being."