Salman told that when Allah's Messenger ﷺ was questioned about clarified butter, cheese and wild asses he replied, “What is lawful is what Allah has declared lawful in His Book, what is unlawful is what Allah has declared unlawful in His Book, and what He has said nothing about belongs to the things He ignores.” Ibn Majah and Tirmidhi transmitted it, Tirmidhi saying this is a gharib tradition which, according to the soundest opinion, is mauquf.