Sayyiduna Abdullah bin Qurt (may Allah be pleased with him) says that the Messenger of Allah (peace and blessings be upon him) said: "The greatest of all days with Allah is the day of sacrifice, then the day of al-Qarr, which is the one that follows it." The narrator says: Five or six sacrificial camels were brought to the Messenger of Allah (peace and blessings be upon him), and they began drawing close to him (as if to see) with which of them he would begin. When they fell on their sides, he (peace and blessings be upon him) spoke softly. I did not understand it, so I asked the person next to me: What did the Messenger of Allah (peace and blessings be upon him) say? He said: He (peace and blessings be upon him) said: "Whoever wishes may cut off (a portion)."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 10239