Ibrahim (may Allah have mercy on him) said that Aswad (may Allah have mercy on him) sent his slave to Sayyidah Aishah (may Allah be pleased with her) to ask about sacrificial camels: should they be taken to stand at Arafah? She said: If you wish, do so; and if you do not wish, then do not.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 10178