Is it permissible to choose a sacrificial animal while it is alive, then not take possession of it until after its slaughter, paying only the price of the pure meat, and not bearing responsibility for it if it dies before slaughter or if its illness becomes apparent afterward?

The sacrifice (udhiyah) is not valid if it is by weight, because one of its conditions is that it must be a sheep complete in its creation and free from defects that prevent its validity. Missing organs, such as a cut ear, or horn, or tail, prevent its validity. Therefore, a specific sheep that meets the conditions of the udhiyah must be purchased for the sacrifice to be valid.