How is the obligation of Hajj performed?

Muḥammad b. Kathīr > Sulaymān b. Kathīr > al-Zuhrī > Sinān > Ibn ʿAbbās

The Messenger of Allah, peace be upon him, said, "Hajj (pilgrimage) has been ordained upon you." It was said, "O Messenger of Allah, is it obligatory every year?" He said, "No, if I had said it was obligatory to perform Hajj every year, it would have become obligatory and anything beyond that would be voluntary." – Weak Chain

حَدَّثَنَا مُحَمَّدُ بْنُ كَثِيرٍ حَدَّثَنَا سُلَيْمَانُ بْنُ كَثِيرٍ عَنْ الزُّهْرِيِّ عَنْ سِنَانٍ عَنْ ابْنِ عَبَّاسٍ قَالَ

قَالَ رَسُولُ اللَّهِ ﷺ «كُتِبَ عَلَيْكُمُ الْحَجُّ» فَقِيلَ يَا رَسُولَ اللَّهِ فِي كُلِّ عَامٍ؟ قَالَ «لَا وَلَوْ قُلْتُهَا لَوَجَبَتْ الْحَجُّ مَرَّةٌ فَمَا زَادَ فَهُوَ تَطَوُّعٌ» – إسناده ضعيف