Musnad Ahmad 30:3476

Yazid narrated to us, Ar-Rabi’ ibn Muslim al-Qurashi informed us, from Muhammad ibn Ziyad, from Abu Hurairah, who said: He addressed us—and once he said: The Messenger of Allah (ﷺ) addressed us—and said: "O people, indeed Allah, the Almighty and Majestic, has made Hajj obligatory upon you, so perform Hajj." A man said: "Is it every year, O Messenger of Allah?" He remained silent until he had said it three times. Then the Messenger of Allah (ﷺ) said: "If I had said 'yes,' it would have become obligatory, and you would not have been able to do it." Then he said: "Leave me as I have left you, for those who were before you were only destroyed by their excessive questioning and their disagreement with their prophets. So if I command you to do something, perform of it as much as you are able, and if I forbid you from something, then leave it."