 According to scholars such as Joseph Schacht, Ignaz Goldziher, and Daniel W. Brown, early schools of Islamic jurisprudence used rulings of the Prophet's Companions, the rulings of the Caliphs, and practices that “had gained general acceptance among the jurists of that school”.On his deathbed, Caliph Umar instructed Muslims to seek guidance from the Quran, the early Muslims ("muhajirun") who emigrated to Medina with Muhammad, the Medina residents who welcomed and supported the "muhajirun" (the "ansar"), the people of the desert, and the protected communities of Jews and Christians ("ahl al-dhimma").According to the scholars Harald Motzki and Daniel W. Brown the earliest Islamic legal reasonings that have come down to us were "virtually hadith-free", but gradually, over the course of second century A.H. "the infiltration and incorporation of Prophetic hadiths into Islamic jurisprudence" took place.