The Prophet ﷺ said, "The greatest of days before Allah is the Day of Sacrifice, then the Day of Settlement."Isa said that Thawr explained that this is the second day.He said, five or six sacrificial camels were brought close to the Messenger of Allah ﷺ, and they began pressing toward him, each one wanting to be the first slaughtered. When they fell on their sides, he spoke a quiet word that I did not catch.I asked, "What did he say?"He replied, "He said, 'Whoever wishes may cut off a portion.'"
حدثنا إبراهيم بن موسى الرازي أخبرنا عيسى ح و حدثنا مسدد أخبرنا عيسى وهذا لفظ إبراهيم عن ثور عن راشد بن سعد عن عبد الله بن عامر بن لحي
عن النبي ﷺ قال إن أعظم الأيام عند الله تبارك وتعالى يوم النحر ثم يوم القر قال عيسى قال ثور وهو اليوم الثاني وقال وقرب لرسول الله ﷺ بدنات خمس أو ست فطفقن يزدلفن إليه بأيتهن يبدأ فلما وجبت جنوبها قال فتكلم بكلمة خفية لم أفهمها فقلت ما قال قال من شاء اقتطع
Its isnad is sahih. Ahmad narrated it, 4:350, from the hadith of Thawr with the same wording. Ibn Khuzayma graded it sahih, 2917h: 2866, 2966, as did Ibn Hibban, 1044h, and Hakim, 4:221, with Dhahabi agreeing with him, while Bayhaqi graded it hasan, 7:288.