After Muhammad ibn Hanafiyya's death, some of his followers, called Karbiyya, came to believe that Muhammad had not died, but was in concealment at a mountain near Medina; and would reappear again as a Mahdi, to fill the world with justice. Another group, called Hashemiyya, maintained that Muhammad ibn Hanafiyya had died in the mountain and has given the Imamate to his son Abu Hashim. All Keysaniyya sects are distinguished by the love for Ali and his family and hatred for ruling dynasty. According to Abd al-Jabbar ibn Ahmad, after Muhammad ibn Hanafiyya's death, some Kaysanites joined Zayn al-Abidin. It was around this time that the doctrine of Nass, (the Imam's explicit designation of his successor) got its importance in Shia Fiqh.