“ And you, under any circumstances, keep yourselves from the devoted thing, lest having devoted it you take of the devoted thing. So would you make the camp of Israel devoted and bring trouble to it.”
The warning is severe. They were devoting the city to YHWH and all were to ensure they did not take for themselves anything they had devoted, for by bringing it into any part of the camp of Israel they would make that part of the camp also ‘devoted to YHWH' and all in it would have to be slain.