Mishnà su Middot 2:7

The area within the wall [of Jerusalem] is holier, for it is there that lesser holy things and second tithe may be eaten. The Temple Mount is holier, for zavim, zavot, menstruants and women after childbirth may not enter it. The chel is holier, for neither non-Jews nor one who contracted corpse impurity may enter it. The court of women is holier, for a tevul yom may not enter it, though he is not obligated a hatat for doing so. The court of the Israelites is holier, for a man who has not yet offered his obligatory sacrifices may not enter it, and if he enters he is liable for a hatat. The court of the priests is holier, for Israelites may not enter it except when they are required to do so: for laying on of the hands, slaying or waving.