Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) said: The Messenger of Allah (peace and blessings be upon him) said to me: "Learn knowledge and teach it to the people, learn the knowledge of obligations (fara'id) and teach it to the people, learn the Qur'an and teach it to the people. Surely, I am about to pass away and knowledge will diminish, tribulations will appear until two men will differ regarding an obligation (fard) and there will not be anyone who can decide between them."