פירוש על קידושין 92:7

Why not say that the hallah separated from flour belongs to the priest, but the dough still has to have terumah removed from it before the dough can be eaten. This would be the like the case of one who separates terumah from a perforated pot for produce in an unperforated pot. The produce in the unperforated pot must still be tithed, but that which was set aside is terumah and belongs to the priest.