Several Quranic verses state that some revelations have been abrogated and superseded by later revelations, and narrations from Muhammad's companions mention abrogated verses or rulings of the religion. The principle of abrogation of an older verse by a new verse in the Quran, or within the hadiths is an accepted principle of all four Sunni "maḏāhib" or schools of "fiqh" (jurisprudence), and was an established principle in Sharia by at least the 9th century, (though since the 19th century, modernist and Islamist scholars have argued against the concept of "naskh", defending the absolute validity of the Quran).