Nafi' narrated that Abdullah bin Umar (may Allah be pleased with them both) said: The sacrificial animal (hady) is that which is garlanded, marked (ish'ar), and taken to stand at Arafah. [Sahih. Recorded by Malik: 849]
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 10174