Allah, Most High, has decreed Hajj for you. Al-Aqra' bin Habis At-Tamimi said: "Every year, O Messenger of Allah?" But he remained silent, then he said: "If I said yes, it would become obligatory, then you would not hear and obey. Rather it is just one Hajj."
Sunan an-Nasa'i Book 24, Hadith 2
← Previous Hadith "The Messenger of Allah addressed the people and said: 'Allah, the Mighty and Sublime, has enjoined upon you Hajj.' A man said: 'Every year?' He remained silent until he had repeated it three times. Then he said: 'If I said yes, it would be obligatory, and if it were obligatory you would not be able to do it. Leave me alone so long as I have left you alone. Those who came before you were destroyed because they asked too many questions and differed with their prophets. If I command you to do something then follow it as much as you can, and if I forbid you to do something then avoid it."'

Sunan an-Nasa'i Book 24, Hadith 1 Next Hadith → "O Messenger of Allah, my fater is an old man and he cannot perform Hajj or 'Umrah, nor can he travel." He said: "Perform Hajj and 'Umrah on behalf of your father."(sahih)

Sunan an-Nasa'i Book 24, Hadith 3