His compassion encompassed not only human beings, but also animals.
The Prophet ﷺ forbade his companions to keep the unintelligent creatures hungry or thirsty, to disturb or to overburden them. He commended that kindness and putting them at ease were meritorious acts tending to bring man nearer to Allah. Abu Hurairah reports the Prophet as saying: "A traveler who was thirsty saw a well in the way. He got inside the well and when he came out he saw a dog licking mud due to thirst. The man realised that the dog was as thirsty as him, so he got into the well again, filled his leather sock with water and carried it out holding it with his teeth. Thus, he quenched the thirst of the dog. Allah was pleased with this act of kindness and pardoned his sins." The Companions asked: "O Messenger of Allah ﷺ is there recompense in the matter of beasts and wild animals also?" The Prophet replied: "There is recompense in regard to every creature that has a living heart." Sahih al-Bukhari 2466 ( Vol. 3, Book 43, Hadith 646)
'Abdullah bin 'Umar related that the Prophet said: "A woman was cast away to hell only because she had withheld food and water from her cat and refused to set it free so that the cat might satisfy its hunger by eating worms and insects." Sahih al-Bukhari 3318 (Vol. 4, Book 54, Hadith 535)
Once on return from a military campaign, a few Companions took away the chicks of a bird from their nest to stroke them. The mother bird came back and when it could not find its chicks in the nest, it began to fly around screeching. When informed of the matter, Allah’s Messenger became angry and ordered the chicks to be put back in the nest. Abu Dawud 2675
I entered upon al-Hakam b. Ayyub along with Anas. He saw some youths or boys who had set up a hen and shooting at it. Anas said: The Messenger of Allah (ﷺ) forbade to kill an animal in confinement. SunanAbiDawud 2816 (Book 15, Hadith 2810)
A Companion, Shaddaad bin 'Aws reported the Apostle as saying: "Allah has commanded you to show kindness to everyone(including animals), so if you have to kill, kill in a good manner, and if you slaughter an animal, slaughter it gently. If anyone of you has to slay an animal, he should sharpen the blade first and treat the animal well. Sahih Muslim 1955 " Ibn 'Abbas relates that a man threw a goat on its side and then started sharpening his knife. When the Prophet saw him he said: "Do you want to kill it twice? Why did you not sharpen the knife before throwing it on the ground?" Tabrani Vol4: 53