Hajj (pilgrimage to the House of Allah) has been made incumbent upon you, so perform Hajj
Abu Hurairah (May Allah be pleased with him) reported:
The Messenger of Allah, may the peace and blessings of Allah be upon him, 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, may the peace and blessings of Allah be upon him, remained silent till the man repeated it thrice. Then he, may the peace and blessings of Allah be upon him, 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, avoid it." [Muslim].
It was narrated in another chain of narrators on the authority of ibn Abbas may Allah be pleased with them and some parts of it were compiled by Al-Bukhari 6858 and Muslim 1337.
This Hadeeth entails one of the most important lessons i.e. politeness with Allah and with His Messenger (peace and blessings of Allah be upon him). We are to abide by the legislation of Allah, so that we do not go beyond it, we are to commit ourselves to what he made obligatory upon us without trespassing the limits. We may not come closer to what he made forbidden for us.
This Hadeeth puts the believer on the straight path, keeps him distant from the degraded matters, it warns him of extremism in religion and asking about the matters Allah has not mention and did not clearly state whether it is lawful or unlawful, or did not specify to the people a limit to which they refer, with no time or place to do or to stop doing it.
What Allah has explained in his book, or so did the Prophet (peace and blessings of Allah be upon him), we may not trespass it, rather we have to commit ourselves to obey him, not to go beyond it to others, not to increase or decrease from it. We may not ask about what Allah and His Messenger (peace and blessings of Allah be upon him) did not mention. We may ask in case we need understand or if we need to know the decisive opinion about a certain topic.