Sayyiduna Anas bin Malik (may Allah be pleased with him) narrates: We were forbidden from asking the Prophet (peace and blessings of Allah be upon him) about anything. So we used to wish that a Bedouin would come to the Prophet (peace and blessings of Allah be upon him) and ask him a question, so we could listen to it. Once, a Bedouin came to the Prophet (peace and blessings of Allah be upon him). He said: O Muhammad (peace and blessings of Allah be upon him), your messenger came to us. He said: You say that Allah Almighty has sent you. The Prophet (peace and blessings of Allah be upon him) said: He spoke the truth. The man asked: Who created the sky? The Prophet (peace and blessings of Allah be upon him) replied: Allah Almighty. He asked: Who created the earth? The Prophet (peace and blessings of Allah be upon him) replied: Allah Almighty. He asked: Who set up these mountains? The Prophet (peace and blessings of Allah be upon him) replied: Allah Almighty. He asked: Who placed benefits in them? The Prophet (peace and blessings of Allah be upon him) replied: Allah Almighty. He said: Then by the One who created the heavens and the earth, and set up the mountains, and placed benefits in them, I ask you (by His name), did Allah Almighty send you? The Prophet (peace and blessings of Allah be upon him) replied: Yes. He said: Your messenger told us that it will be obligatory for us to pray five prayers (daily). The Prophet (peace and blessings of Allah be upon him) said: He spoke the truth. He asked: By the One who sent you, did Allah Almighty command you this? The Prophet (peace and blessings of Allah be upon him) replied: Yes! He said: Your messenger told us that paying zakat from our wealth will be obligatory. The Prophet (peace and blessings of Allah be upon him) said: He spoke the truth. The man said: By the One who sent you, did Allah Almighty command you this? The Prophet (peace and blessings of Allah be upon him) said: Yes! He said: Your messenger also told us that fasting for one month in the whole year will be obligatory upon us. The Prophet (peace and blessings of Allah be upon him) said: He spoke the truth. The man said: I ask you by the One who sent you, did Allah Almighty command you this? The Prophet (peace and blessings of Allah be upon him) said: Yes!

(Imam Ibn Hibban, may Allah have mercy on him, says: Rulings of this nature, such as wudu, tayammum, ghusl janabah, five prayers, obligatory fasting, and other such rulings, are obligatory upon the addressed individuals in some circumstances, not in all circumstances.)