John Burton argues that naskh was first employed by Islamic scholars ("usulis") in the second century of Islam working to develop principles ("usul al-fiqh") for the Islamic law (fiqh) and seeking to explain why some fiqh rulings were not founded on Quranic/Sunnah revelation. By this time the Islamic empire spanned three continents and fiqh had been established in the different regions but usulis found rulings in certain verses of the Quran and parts of the Sunnah had been ignored in their formulation. To explain this, Burton argues, they developed the concept of naskh to declare that the verses/parts had been abrogated.