You thinking of this?
Deuteronomy 23:12-13
Also you shall have a place outside the camp, where you may go out; and you shall have an implement among your equipment, and when you sit down outside, you shall dig with it and turn and cover your refuse.
The Law is spiritual.
Natural first, then spiritual (1 Cor. 15:44-46).
Exo_29:14 But the flesh of the bullock, and his skin, and his dung, shalt thou burn with fire without the camp: it is a sin offering.
Lev_4:12 Even the whole bullock shall he carry forth without the camp unto a clean place, where the ashes are poured out, and burn him on the wood with fire: where the ashes are poured out shall he be burnt.
Lev_4:21 And he shall carry forth the bullock without the camp, and burn him as he burned the first bullock: it is a sin offering for the congregation.
Lev_8:17 But the bullock, and his hide, his flesh, and his dung, he burnt with fire without the camp; as the LORD commanded Moses.
Lev_16:27 And the bullock for the sin offering, and the goat for the sin offering, whose blood was brought in to make atonement in the holy place, shall one carry forth without the camp; and they shall burn in the fire their skins, and their flesh, and their dung.
Psa_83:10 Which perished at Endor: they became as dung for the earth.
Jer_8:2 And they shall spread them before the sun, and the moon, and all the host of heaven, whom they have loved, and whom they have served, and after whom they have walked, and whom they have sought, and whom they have worshipped: they shall not be gathered, nor be buried; they shall be for dung upon the face of the earth.
Jer_9:22 Speak, Thus saith the LORD, Even the carcases of men shall fall as dung upon the open field, and as the handful after the harvestman, and none shall gather them.
Zep_1:17 And I will bring distress upon men, that they shall walk like blind men, because they have sinned against the LORD: and their blood shall be poured out as dust, and their flesh as the dung.
Rev_19:20 And the beast was taken, and with him the false prophet that wrought miracles before him, with which he deceived them that had received the mark of the beast, and them that worshipped his image. These both were cast alive into a lake of fire burning with brimstone.
Rev 20:9 And they went up on the breadth of the earth, and compassed the camp of the saints about, and the beloved city: and fire came down from God out of heaven, and devoured them.
The ways of the world, self-righteousness, are as "dung":
Php_3:8 Yea doubtless, and I count all things but loss for the excellency of the knowledge of Christ Jesus my Lord: for whom I have suffered the loss of all things, and do count them but dung, that I may win Christ,