 the prophet stayed silent and the guy asked again how many times should we come to hajj he stayed silent three times afterwards the prophet answered he told him if i told you you should come every year it would have been an obligatory thing and no one would be able to do it so the required is once but just from the questioning and the response of the prophet it tells you that if he could have said come every year maybe he would have but that would be too much for many many people so we're required to do one