Sahih Muslim Book 7, Hadith Number 3027.

Chapter : It is permissible to join seven persons in a cow or a camel.

Jabir b. ‘Abdullah (Allah be pleased with them) reported: We joined Allah’s Apostle (may peace be upon him) in Hajj and Umra and seven persons shared in the sacrifice of an animal. A person said to Jabir (Allah be pleased with him): Can seven persons share in the sacrifice of al-Badnah (a camel) as he shares in al-Jazur (a cow)? He, (Jabir) said: It (al-Jazur) is nothing but one among the budun. Jabir was present at Hudaibiya and he said: We sacrificed on that day seventy camel, and seven men shared in each sacrifice (of camel).