It is narrated from Sayyiduna Hudhayfah (may Allah be pleased with him), he says: We were sitting in the service of the Noble Prophet (peace and blessings be upon him), and he (peace and blessings be upon him) said: I do not know how long I will remain among you. Then he (peace and blessings be upon him) pointed towards Sayyiduna Abu Bakr and Sayyiduna Umar (may Allah be pleased with them) and said: After me, follow these two, hold firmly to the era of Ammar, and affirm whatever Abdullah bin Mas'ud tells you.