Sayyiduna Abdullah bin Amr (may Allah be pleased with them both) narrates that a man came to the service of the Messenger of Allah (peace and blessings be upon him) and began to submit... and he narrated this hadith, and in it was also that the Prophet (peace and blessings be upon him) said: "There is reward for (kindness to) every living being with a moist liver."
Hadith Referenceمسند الشهاب / 114
Hadith Gradingمحدثین:إسناده حسن
Hadith Takhrij«إسناده حسن ، و أخرجه أحمد : 223/2»
Brief Explanation
Explanation: Please observe the background of this hadith:
The Messenger of Allah sallallahu alayhi wa sallam said: "A man was walking when he felt intense thirst. He descended into a well and drank water. Then, when he came out, he saw a dog panting and licking mud out of thirst. He thought to himself that this dog is suffering from the same thirst that I was just experiencing. So, he went down into the well, filled his leather sock with water, held it in his mouth, and climbed up, then gave the dog water to drink. Allah accepted this deed of his and forgave him." The Companions radi Allahu anhum asked: O Messenger of Allah! Is there a reward for us in (serving) animals as well? He sallallahu alayhi wa sallam replied: "There is a reward in (serving) every living being with a moist liver." (Bukhari: 2363)
Sayyiduna Suraqah bin Ja‘tham radi Allahu anhu asked: Someone’s lost camel comes to my pond, which I have prepared for my own camels. If I give that camel water there, will I get a reward? He sallallahu alayhi wa sallam replied: "Yes, there is a reward in (serving) every living being with a warm liver." (Ibn Majah: 3686, Sahih)
The meaning of the hadith is absolutely clear: there is a reward in serving every living creature.