From this hadith, it is understood that one should not ask questions without necessity. When the Messenger of Allah (sallallahu alayhi wa sallam) said that Hajj is obligatory upon you, in one narration it is mentioned that he (sallallahu alayhi wa sallam) remained silent, then said that if I had said that Hajj is obligatory every year, it would have become obligatory, and then you would not have been able to perform Hajj every year, and if you did not perform Hajj every year, you would have been punished (for abandoning Hajj). Making something obligatory and binding is from Allah Ta'ala, but if you (sallallahu alayhi wa sallam) had said yes, then the same command would have been issued from Allah. This too is a supreme example of the mercy and kindness of Muhammad (sallallahu alayhi wa sallam), the Mercy to the Worlds, upon his Ummah.