מדרש אויף ויקרא 6:4

Variantly: "You may not light a fire in all of your dwellings": From (Leviticus 6:6) "A perpetual fire shall burn on the altar," I might think, both on the weekdays and on the Sabbath. And how would I understand (Exodus 31:14) "Those who profane it shall be put to death"? As referring to other labors, other than that of (lighting) the woodpile. (But perhaps, even the woodpile.) And how would I understand (Leviticus 6:4) "It (the woodpile fire) shall not go out"? As referring to weekdays, and not the Sabbath. It is, therefore, written "You may not light a fire in all of your dwellings." For your dwellings you do not light it, but you do light it for the Temple (woodpile).

4) And when it is written in respect to the ashes (Vayikra 6:4): "outside the camp," let this not be stated, for it is already written (here): "to a clean place, where the ashes are poured out." If so, why is "outside the camp" written? To add a third camp.

5) (But now we have a) kal vachomer (a fortiori argument) that the zav is subject to mishkav tumah above him (when there are on his head things that are fit for mishkav beneath him), viz.: If beneath him, where Scripture did not make things subject to middaf tumah, it made him subject to mishkav tumah, then (above him), where Scripture made things subject to middaf tumah, how much more so should they be subject to mishkav tumah! It is, therefore, written (Vayikra 6 verse 4) "Every mishkav on which the zav lies down shall be tamei" — He confers mishkav (tumah) beneath him and not above him.