Musnad Abu Ya'la al-Mawsili 3:257

Abu Sa'id narrated to us, Mansur ibn Wardan narrated to us, Ali ibn Abd al-A'la narrated to us, from his father, from Abu al-Bakhtari, from Ali, who said: When "And [due] to Allah from the people is a pilgrimage to the House - for whoever is able to find thereto a way" (Al Imran: 97) was revealed, the believers said: "O Messenger of Allah, is it every year, twice?" He said: The Messenger of Allah, peace and blessings of Allah be upon him, remained silent. They said: "O Messenger of Allah, is it every year, twice?" He said: "No. And had I said 'yes,' it would have become obligatory." Then Allah revealed: "O you who have believed, do not ask about things which, if they are shown to you, will distress you" (Al-Ma'idah: 101).