Question: Is it permissible to keep a dog as a pet in my house?
Answer: It is better not to, and its preferable to choose another animal as a pet, as a dog is ritually impure (Najis) according to Islamic law, and thus it would cause one to live with considerable difficulty. It's also been mentioned that prayers in a place with a dog around is abominable (Makrooh).
Ayatollah Al-Sayyid Ali Al-Husseini Al-Sistani