It was narrated that Ibn 'Abbas (رضي الله عنه) said: The Messenger of Allah (ﷺ) addressed us and said:

"O people, Hajj has been prescribed for you," al-Aqra’ bin Habis stood up and said: Is it every year, O Messenger of Allah? He said: “If i said that, it would become obligatory, and if it became obligatory, you would not do it and you would not be able to do it. Hajj is once (in a lifetime) and whoever does more, it is voluntary."