Firstly: Definition of the Mass Circumambulation
Ifadah means proceeding and marching in mass procession. It only applies in the contexts of dispersal and gathering. The original meaning is to pour, but the word was later applied to marching in procession. Related to this last meaning is Tawaf al-Ifadah (the Mass Circumambulation) on the Day of Eid al-Adha. People pour out of Mina to Mecca, perform circumambulation, and then return.
Secondly: Names for the Mass Circumambulation
The Mass Circumambulation has many names, including:
Tawaf al-Ifadah, so named because it follows the pouring out of Mina to Mecca.
Tawaf al-Ziyarah, so named because pilgrims leave Mina to visit the Ka`bah but do not reside in Mecca. Rather, they return to Mina. Ziyarah means a visit.
Tawaf al-Sadar, so named because it is performed after returning. Sadar means departure. Sadar also refers to the Farewell Circumambulation.
Tawaf al-Wajib, Tawaf al-Rukn, and Tawaf al-Fard, so named because of the ruling related to it.
Thirdly: The Ruling of the Mass Circumambulation
The Mass Circumambulation is a rukn of Hajj without which Hajj is invalid and for which there is no substitute. Consensus regarding it being a rukn was related by Ibn al-Mundhir, Ibn Hazm, Ibn `Abd al-Barr, al-Nawawi, and Ibn Taymiyyah.
Fourthly: The Mass Circumambulation must follow `Arafah
The Mass Circumambulation must be preceded by standing at `Arafah. If one performs the Mass Circumambulation before standing at `Arafah, one is not absolved of the fard performance of circumambulation. Ibn Taymiyyah related consensus on this.
Fifthly: The Sunnah Time to Perform the Mass Circumambulation
It is sunnah to perform the Mass Circumambulation at the start of the Day of Eid al-Adha, after pelting, slaughtering, and shaving. This is the best time to begin its performance. Consensus on this was related by al-Nawawi.
Sixthly: The Starting Time for the Mass Circumambulation
Scholars have differed regarding the starting time for the Mass Circumambulation. There are two positions:
The first position: The starting time for the Mass Circumambulation is after half the night of Eid al-Adha has passed for those who have already stood at `Arafah. This is the position of the Shafi`i and Hanbali schools. This is the chosen position of Ibn Baz.
The second position: It starts with the appearance of true dawn on the Day of Eid al-Adha. This is the position of the Hanafi and Maliki schools. It is also one narration from Ahmad.
Seventhly: Performing the Mass Circumambulation during the Days of Tashreeq
If one delays the Mass Circumambulation until after Eid al-Adha and performs it during the Days of Tashreeq, their circumambulation is valid and nothing is due of them. Consensus on this was related by Ibn al-Mundhir and al-Nawawi.
Eighthly: The Ending Time for the Mass Circumambulation
The Mass Circumambulaton has no ending time, nor does delaying it necessitate blood.  Hanafis hold that its time extends to the end of one’s life. However, delaying it beyond the Eid al-Adha days and nights is sinful and necessitates blood. This is the position of the Shafi`i and Hanbali schools and the position of a group of the Salaf. This is the chosen position of Ibn Baz. The Permanent Council’s fatwa corresponds to this position.
Ninthly: The Wajib Time for the Mass Circumambulation and the Consequences of Delaying It
Scholars have differed regarding the wajib time for the Mass Circumambulation and what the consequences of delaying it are.  Ibn al-Mundhir says: “I am not aware of them differing that whoever delays the circumambulation past the Day of Eid al-Adha and performs it during the Days of Tashreeq has performed their fard duty and nothing is due of them.” (Al-Ishraf, 3/362) The strongest two positions are:
The first position: It is wajib to perform it before the end of Dhu al-Hijjah. If Dhu al-Hijjah ends, blood is required of him. This is the position of the Maliki school. This is the chosen position of Ibn `Uthaymin.
The second position: Nothing is ever due for delaying it. This is the position of the Shafi`i and Hanbali schools. This is the chosen position of Ibn al-Mundhir and Ibn Baz.
Tenthly: Drinking from Zamzam after Circumambulation
It is sunnah to drink from Zamzam after circumambulation. This is by agreement of the four schools of jurisprudence.  Shafi`is and Hanbalis hold that it is mustahabb to drink from it after the Mass Circumambulation. Hanafis, Hanbalis, and some Malikis hold that it is mustahabb to drink from Zamzam after the Farewell Circumambulation. Ibn `Uthaymin says: “Scholars (may Allah have mercy on them) have differed: did the Messenger ﷺ drink that as an act of worship or because he needed to drink? This is a matter that about which I am hesitant. As for the default ruling of drinking Zamzam, it is sunnah. Therefore, so long as the matter is doubtful as to whether it is an act of worship or disposition, we don’t say that it is legislated unless the Messenger ﷺ commanded it. It is possible that when the Messenger ﷺ circumambulated, he needed to drink. Nothing has reached me indicating that he ﷺ drank after circumambulating for `umrah, whether during the `umrah of Ji`ranah or the `umrah of Qada’. For this reason, there is a very strong possibility that he drank it because he needed to. So those who do not mention this [i.e. drinking Zamzam] do not see it as being legislated, but rather, the Messenger ﷺ merely needed to drink so he did.” (Majmu` Fatawa wa Rasa’il al-`Uthaymin, 23/220)