Why does Islam consider dogs and pigs to be najis (impure), and what is the evidence for this from the Qur’an and Sunnah? What other animals are considered najis?

A non-Muslim might think that God does not create evil, but this is a mistake, for God is the Creator of all things, and He has wisdom in His creation. This includes the creation of Iblis (Satan) and harmful animals. This does not mean that everything God created is pure.

The assertion of the impurity of pigs and dogs is not agreed upon. Imam Malik and Sheikh al-Islam Ibn Taymiyyah hold the view that pigs and dogs are pure as long as they are alive. Some scholars consider dogs impure but not pigs, while others hold the opposite view.

As for Muslims, they distance themselves from dogs for fear of being afflicted by their impure saliva, which requires a special washing seven times, one of them with earth, as stated in the noble Hadith: "The purification of the vessel of one of you, when a dog laps from it, is to wash it seven times, the first of them with earth."