The Messenger of Allah ﷺ addressed us on the Day of Sacrifice while mounted on a red she-camel with a clipped ear, and he said, "This is the Day of Sacrifice, and this is the day of the greatest Hajj."
خطبنا رسول الله ﷺ يوم النحر على ناقة له حمراء مخضرمة، فقال: هذا يوم النحر، وهذا يوم الحج الأكبر.
Ahmad (1588) narrated it from Waki, who said, Shuba told us, from Amr bin Mura, from Mura Tayyib, who said, A man from among the companions of the Prophet ﷺ told me in this upper room of mine, I think he said (and he related it). Its isnad is sahih. Amr bin Mura is Ibn Abdullah bin Tariq Jamali Muradi, one of the men accepted by the whole community. Mura Tayyib is Ibn Sharahil Hamdani, Abu Ismail Kufi, called Mura Tayyib, one of the men accepted by the whole community.On this subject there is also what was reported from Amr bin Ahwas, that he was present at the Farewell Hajj with the Messenger of Allah ﷺ, who praised Allah and extolled Him, spoke and admonished, then said, "Which day is the day of forbidding? Which day is the day of forbidding? Which day is the day of forbidding?" The people said, "The day of the Greater Hajj, O Messenger of Allah." He said (and he related the rest of the hadith). Tirmidhi (3087) narrated it from Hasan bin Ali Khallal, Husayn bin Ali Jafi told us, from Zaida, from Shabib bin Gharqada, from Sulayman bin Amr bin Ahwas, from his father, and he related it. Sulayman bin Amr is "acceptable" as stated in Taqrib. Ibn Qattan said, "Unknown." This hadith was also narrated by Abu Dawud and Ibn Majah in the sermons of the Prophet ﷺ during the Farewell Hajj. Consult those sources for further references.On this subject there is also what was reported from Ali bin Abu Talib, who said, I asked the Messenger of Allah ﷺ about the day of the Greater Hajj, and he said, "The day of sacrifice." Tirmidhi (3088) narrated it from Abdul-Warith bin Abdul-Samad bin Abdul-Warith, my father told me, from his father, from Muhammad bin Ishaq, from Abu Ishaq, from Harith, from Ali bin Abu Talib, and he related it. He also narrated it from the hadith of Sufyan, from Abu Ishaq, from Harith, from Ali, who said, "The day of the Greater Hajj is the day of sacrifice."Tirmidhi said, "This hadith is more sahih than the hadith of Muhammad bin Ishaq, because this hadith has been narrated through other routes from Abu Ishaq, from Harith, from Ali as a stopped report. We do not know of anyone who raised it to the Prophet except what was reported from Muhammad bin Ishaq. Shuba narrated this hadith from Abu Ishaq, from Abdullah bin Mura, from Harith, from Ali, as a stopped report."I say, along with it being stopped at Ali bin Abu Talib, it also contains Abu Ishaq, who was known to have mixed up his narrations later in life and to practice tadlis, and his teacher Harith, who is Ibn Abdullah Awar Hamdani, about whom there is well known criticism, and he has been accused of lying.The people of knowledge have differed regarding His statement, "the day of the Greater Hajj" [Tawbah 9:3]. It was said that it is the day of Arafah, and it was said that it is the day of sacrifice, and it was said that it is all the days of Hajj. Ibn Jareer, in his tafsir, attributed these sayings to those who held them, then said, "The most correct of these sayings in our view is the saying of those who say that the day of the Greater Hajj is the day of sacrifice, because of the corroborating reports from a group of the companions of the Messenger of Allah ﷺ that Ali proclaimed what the Messenger of Allah ﷺ had sent him to proclaim to the polytheists, and recited to them "Baraah" on the day of sacrifice..." Tafsir Tabari (11/336).