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 f

Jaibir b. 'Abdullah (Allah be pleased with them) reported:

We performed Hajj Tamattu' along with Allah's Messenger (ﷺ) and we slaughtered a cow on behalf of seven persons sharing in it.
حَدَّثَنَا يَحْيَى بْنُ يَحْيَى، أَخْبَرَنَا هُشَيْمٌ، عَنْ عَبْدِ الْمَلِكِ، عَنْ عَطَاءٍ، عَنْ جَابِرِ بْنِ، عَبْدِ اللَّهِ قَالَ كُنَّا نَتَمَتَّعُ مَعَ رَسُولِ اللَّهِ صلى الله عليه وسلم بِالْعُمْرَةِ فَنَذْبَحُ الْبَقَرَةَ عَنْ سَبْعَةٍ نَشْتَرِكُ فِيهَا ‏.‏
Reference : Sahih Muslim 1318 f
In-book reference : Book 15, Hadith 394
USC-MSA web (English) reference : Book 7, Hadith 3029
  (deprecated numbering scheme)