Is it permissible to buy one-seventh of a cow from a butcher as an Udhiyah if the slaughter occurs after the Eid prayer and fulfills the remaining conditions, by analogy with the permissibility of seven people sharing in an Udhiyah despite differing intentions?

The intention of the sacrificer is a prerequisite for the sacrifice (udhiyah), either at the time of slaughter, or before it, or when handing it over to an agent. This is because it is an act of worship, as indicated by the words of Allah Almighty: "Say, 'Indeed, my prayer, my rites of sacrifice...'" (Qur’an 6:162). Therefore, if a person buys a share of a cow that was slaughtered for meat and intends to offer it as a sacrifice, it is not valid. As Imam Ahmad said: "It is meat that he bought, not a sacrifice."