Midrasz do Kapłańska 14:38

6) (Vayikra 14:38) "Then the Cohein shall go out of the house to the door of the house, and he shall shut up the house for seven days": I might think that he could go to his house and shut it up; it is, therefore, written "to the door of the house and he shall shut it up." If "to the door of the house," I might think that he could stand under the lintel and shut it up; it is, therefore, written "out of the house." How so? He stands at the side of the lintel and shuts it up.

7) And whence is it derived that if he (the Cohein) went to his house and shut it up or stood in his house and shut it up, that the shutting up is valid? From "and he shall shut up the house" — in any event.