Mistreating animals is considered a sin in Islam. A Muslim is responsible for the care of animals so much so that an ill-treated animal will testify against the one who abused it on the Day of Judgment. Islam forbids branding animals and killing them in vain, such as for sport. The Prophet Muhammad forbade people to capture birds, burn anthills, and whip animals. Even in slaughtering animals for food, Islam requires that the slaughtering be done according to Islamic procedure, which is humane and aims to cause the animals as little suffering as possible. As humans, we have a responsibility towards every living creature.
Cats in Islam
The Prophet Muhammad taught mercy to all of God's creation. There are many reports of his love for cats resulting in their historical acceptance among Muslims. Cats were very common among the people during the time of the Prophet, and he said,"They (cats) are not impure and they intermingle with you." The cat is such a clean animal that according to authentic narrations one may make ablution for Prayer with the same water that a cat drank from. Yet, it is known that some people nowadays have opposed the traditions of the Prophet by taking up the evil practices of torturing and poisoning cats. In Islam, punishment for such acts is severe. Both Al-Bukhari and Muslim reported a hadith regarding a woman who locked up a cat, refusing to feed it and not releasing it so that it could feed itself. The Prophet Muhammad said that her punishment on the Day of Judgment will be torture and Hell.