Ritual Practices which Permit use of Certain Items - Matirin
Impact of a Matir
One is liable for making a korban impure, or eating it in its impurity, once the matir has been brought: Zevachim 34a
A thought is only effective in rendering an item pigul if the thought takes place during the service of the item's matir - the service which, if performed correctly, permits that item to be used: Zevachim 42b-43b
An entity can be a "matir" if it permits another item to be used for a service, even if it does not permit personal use of that item: Zevachim 44b
Do we consider the blood of the metzora's korban asham a matir for personal use of the oil remnants, since the oil may not be used until the asham's service is complete - or not, since the oil may be brought at a later date: Zevachim 43a, 44a-b