It is narrated from Sayyiduna Ali (may Allah be pleased with him) that when this blessed verse was revealed: "And pilgrimage to the House is a duty owed to Allah by the people, for whoever is able to find a way to it" [Al Imran: 97], the Companions (may Allah be pleased with them) said: "O Messenger of Allah (peace and blessings be upon him), is it obligatory to perform Hajj every year?" He (peace and blessings be upon him) remained silent. They asked again: "Every year?" He (peace and blessings be upon him) said: "No; and had I said 'yes', it would have become obligatory every year." Then Allah, Glorified and Exalted, revealed this verse: "O you who believe, do not ask about things which, if they were made plain to you, would distress you" [al-Ma'idah: 101], to the end of the verse.
Hadith Referenceمسند أبي يعلى الموصلي / مسند علي بن أبي طالب رضي الله عنه / 542
Hadith Takhrij«قال سعيد بن محمد السناري: ضعيف: مضى تخريجه [برقم 517]. ف» «أخرجه سنن الترمذي برقم: 814، 3055، وأخرجه سنن ابن ماجه برقم: 2884، وأخرجه مسند أحمد برقم: 907، وأخرجه فتح الباري برقم: 4345، 6858، 6859، وأخرجه مسند البزار برقم: 913، وأخرجه المستدرك على الصحيحين برقم: 3211، مسند ابویعلیٰ ترقیم الاثری: 537»