Masruq (may Allah have mercy on him) says that we were sitting with Sayyiduna Ibn Mas'ud (may Allah be pleased with him) and he was teaching us the Qur'an. In the meantime, a man came and said: O Abu Abdur Rahman! Did you people ask the Prophet (peace and blessings of Allah be upon him) how many caliphs there will be in this Ummah? Sayyiduna Ibn Mas'ud (may Allah be pleased with him) replied: Since I have come to Iraq, no one before you has asked me this question until today. Then he said: Yes! We did ask the Prophet (peace and blessings of Allah be upon him) this question, and he (peace and blessings of Allah be upon him) said: "There will be twelve caliphs, like the number of chiefs of Bani Israel."