كتاب الحج
15
The Book of Pilgrimage
(62)
Chapter: It is permissible to share in the sacrifice, and a camel or a cow is sufficient for seven people
(62)
باب الاِشْتِرَاكِ فِي الْهَدْىِ وَإِجْزَاءِ الْبَقَرَةِ وَالْبَدَنَةِ كُلٍّ مِنْهُمَا عَنْ سَبْعَةٍ ‏‏
Sahih Muslim 1318 c

Jabir b. 'Abdullah (Allah be pleased with him) reported:

We performed Hajj along with Allah's Messenger (ﷺ), and we sacrificed a camel on behalf of seven persons, and a cow on behalf of seven persons.
وَحَدَّثَنِي مُحَمَّدُ بْنُ حَاتِمٍ، حَدَّثَنَا وَكِيعٌ، حَدَّثَنَا عَزْرَةُ بْنُ ثَابِتٍ، عَنْ أَبِي الزُّبَيْرِ، عَنْ جَابِرِ بْنِ عَبْدِ اللَّهِ، قَالَ حَجَجْنَا مَعَ رَسُولِ اللَّهِ صلى الله عليه وسلم فَنَحَرْنَا الْبَعِيرَ عَنْ سَبْعَةٍ وَالْبَقَرَةَ عَنْ سَبْعَةٍ ‏.‏
Reference : Sahih Muslim 1318 c
In-book reference : Book 15, Hadith 391
USC-MSA web (English) reference : Book 7, Hadith 3026
  (deprecated numbering scheme)