When was Surat al-Hajj revealed, and when was the Hajj prescribed?

The obligation of Hajj was not established by a verse from Surat Al-Hajj, but rather by Allah's saying: ﴿And [due] to Allah from the people is a Hajj to the House - for whoever is able to find thereto a way.﴾ [Aal Imran: 97]. Scholars differed on the date of its فرض (imposition), with some saying it was in the third year, some in the fifth, and some in the ninth year of the Hijra. Imam Al-Shafi'i used this to argue that its obligation is على التراخي (on deferment/not immediate).

Surat Al-Hajj was named as such because Allah mentioned in it Ibrahim's command to call people to perform Hajj to the House and the rituals prescribed therein, despite Hajj being enjoined by verses in Surat Al-Baqarah and Surat Aal Imran. The majority of scholars believe that Surat Al-Hajj is mixed, with some parts being Makkan and others Medinan.