It is narrated from Jabir (may Allah be pleased with him) who states: We performed sacrifice at the place of Hudaybiyyah along with the Messenger of Allah (peace be upon him); the sacrifice of a camel was done on behalf of seven people, and the sacrifice of a cow was also done on behalf of seven people.
Hadith Referenceمسند الإمام الشافعي / كتاب العيدين والأضاحي والاستسقاء / 506
Hadith Takhrijاخرجه مسلم، الحج، باب جواز الاشتراك فى الهدى، واجزاء البدنه والبقرة .... الخ (1318)