Is it permissible to share in the sacrifice of a cow for fewer than seven people?

It is permissible for fewer than seven people to share in one cow for sacrifice (Udhiyah). If it is permissible for seven to share in it, then fewer are even more deserving of permissibility. The sharers would be considered as offering the surplus voluntarily, just as if one person were to sacrifice a whole cow. Al-Shafi'i said: "And if they were fewer than seven, it would suffice for them, and they are offering the surplus voluntarily." Al-Kasani said: "And there is no doubt about the permissibility of a large camel (badanah) or a cow for fewer than seven; because since a seventh is permissible, then more is even more fitting."