BT Git 68b(52) :וליתלי בסיפיה דבבא ד̇כ̇י עייל חייף ביה וכי נפיק חייף ביה‏ : let him hang it on the door post so that when he comes in he rubs against it and when he goes out he rubs against it
See the entire entry for ḥpp vb. to wash