Sayyiduna Abu Hurairah (may Allah be pleased with him) narrates: Once, while the Prophet Muhammad (peace and blessings be upon him) was delivering a sermon, he said: O people! Indeed, Allah the Exalted has made Hajj obligatory upon you. A man stood up and asked: O Messenger of Allah (peace and blessings be upon him)! Is it every year? The narrator says: The Prophet (peace and blessings be upon him) did not answer him, until the man repeated his question three times. Then the Prophet (peace and blessings be upon him) said: If I had said yes, it would have become obligatory, and if it had become obligatory, you would not have been able to do it. Leave me with what I leave you about; for those before you were destroyed only because of their excessive (unnecessary) questioning of their prophets and their disagreements with them. When I forbid you from something, then avoid it, and when I command you to do something, then do it as much as you are able. He also mentioned that the following verse in Surah Al-Ma'idah was revealed regarding this: "O you who believe! Do not ask about things which, if made plain to you, may cause you trouble."