Sayyiduna Abdullah bin Qurt (may Allah be pleased with him) says that the Messenger of Allah (peace and blessings be upon him) said: "The best of days with Allah is the day of sacrifice, then the day of al-Qarr, on which the people stay settled," that is, the day that follows the day of sacrifice. Five or six sacrificial camels were brought forward 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, the Messenger of Allah (peace and blessings be upon him) said something softly that I did not understand. I said to the person at my side: What did he (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 / 10214