R. Yossi b. R. Yehudah says: From half the altar northwards is regarded as north, and from half the altar southwards is regarded as south. And this tells me only that the north of the altar is kasher for slaughtering. Whence do I derive (the same for) all the north of the azarah (the Temple court)? From (Leviticus 14:13) "And he shall slaughter the lamb in the place where he shall slaughter the sin-offering and the burnt-offering, in the holy place." Let this not be written. (Why is it written?) To render kasher the entire northern side (of the azarah)?