Sayyiduna Jabir bin Abdullah (may Allah be pleased with him) says, concerning the Hajj of the Messenger of Allah (peace and blessings be upon him), his telling the people to perform Umrah and leave ihram, his sermon, and his saying: "If I had known beforehand what I came to know later, I would not have brought the sacrificial animal, and I would have left ihram like the people. So whoever has no sacrificial animal should fast three days during Hajj and seven days on returning home, and whoever has a sacrificial animal available should slaughter it": We used to slaughter one camel on behalf of seven persons. And he mentioned the whole hadith.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 8891