Abu Hurairah (May Allah be pleased with him) reported: The Messenger of Allah (PBUH) delivered a Khutbah and said, "O people! Hajj (pilgrimage to the House of Allah) has been made incumbent upon you, so perform Hajj." A man inquired: "O Messenger of Allah, is it prescribed every year?" He (PBUH) remained silent till the man repeated it thrice. Then he (PBUH) said, "Had I replied in the affirmative, it would have surely become obligatory, and you would not have been able to fulfill it." Afterwards he said, "Do not ask me so long as I do not impose anything upon you, because those who were before you were destroyed on account of their frequent questioning and their disagreement with their Prophets. So when I order you to do something, do it as far as you can; and when I forbid you from doing anything, eschew it."