Do not cause them harm!

All religions promote peace and dignity, mutual respect, justice and mercy. And the most valuable of these qualities is mercy. “We have sent you (O Prophet) only as a mercy for the whole world.” (Sura Al Anbiya, ayah 107) Mercy is a quality that expresses kindness, piety, caring, respect, love and forgiveness. These qualities are a reflection of the grace of the Almighty in relation to His creations in this world.
The Prophet (peace and blessings be upon him) was the epitome of mercy, which was shown towards everyone who surrounded him: loved ones, friends, strangers and even enemies. He treated the environment, animals, insects, plants with respect and mercy as well, since this whole world, with all its diversity, is the creation of the Creator, the personification of His wisdom and power.
The Messenger of the Lord (peace and blessings be upon him) taught his followers to treat the creations of the Most High with dignity and care.
Abu Hurayrah (may God be pleased with him) reported that the Messenger of God (peace and blessings be upon him) said, “While a man was proceeding on his way he became extremely thirsty. He found a well and went down into it to drink water. Upon leaving it, he saw a dog which was panting from thirst.
His tongue was lolling out and he was eating moist earth because of his extreme thirst. The man thought to himself, ‘This dog is as extremely thirsty as I was.’ So he descended into the well, filled up his leather sock with water and, holding it in his teeth, climbed up and quenched the dog’s thirst. God appreciated his action and forgave his sins.”
The Companions asked, “Shall we be rewarded for showing kindness to animals also?” The Prophet (peace and blessings be upon him) said, “A reward is given in connection with every living creature [lit. everything with a moist liver].” (Narrated by alBukhari, Muslim).
Imam al Nawawi in the book “Al Minhaj fi sharh Sahih Muslim” (“Interpretation of the Collection of Reliable Hadith”) writes, “The expression ‘a reward is given in connection with everything with a moist liver’ means that a person will get a reward from God for showing kindness and care to every living being. And a living being is called the owner of a moist liver because the body of the dead is dry.”
It is important to note that this hadith contains an indication of showing mercy to every animal, even if it is not our own property. After all, the dog that the man met in the desert was not his own.
In his commentary on this hadith, Imam Ibn Abd ul Barr alMaliki said, “This hadith contains an argument defending the fact that causing harm, or suffering to animals is unacceptable, and the one who commits such a thing falls into sin. Since the text says that a person gets reward for a kind attitude towards all living things, he will be responsible for causing any harm to them. Moreover this act will be recorded as a sin.”
Imam Ibn al Mulyakkin, in his commentary on this hadith, said, “This does not contradict the fact that there are those among the animals whom we are commanded or allowed to kill. This is since this killing is lawful because of its predominant benefit. And at the same time we are commanded to carry out the killing in a good, humane way.”
Abdullah ibn Umar (may God be pleased with him) reported that the Messenger of the Almighty (peace and blessings be upon him) said, “A woman was punished due to a cat she had imprisoned until it died, so she entered Hellfire. She did not give it food or water while it was imprisoned, neither did she set it free to eat from the vermin of the earth.” (Narrated by al Bukhari and Muslim)
Just imagine: the Almighty punished this woman with Hell because she deprived the cat of freedom, refused to feed and drink it and did not let it out of the house to search for food on its own.