In Masechet (tractate) Avodah Zarah, Perek Dalet (Chapter Four), Mishnah Vav, the Mishnah says, “Avodah Zarah (idol worship) shehinichuha ovdeha.” If an idol that was being worshipped was eventually abandoned, the people who owned it moved away and left it behind, and there doesn’t seem to be any plan to return to it, b’sha’at shalom muteret: if it happened during a time of peace, then the idol is permitted to benefit from. The fact that they left doesn’t suggest that they were in any hurry; it wasn’t as if they were running away from somebody. There was peace. So it proves that they don’t want it anymore and that it’s now nullified. B’sha’at milchama asura: if it happened in a time of war, it’s prohibited. It is very possible that they left it behind because they were fleeing, they were running away from the war, and that’s why it got left behind.
Bimosi’ot shel melachim hare elu mutarot: if there are pedestals set up in honor of the king, on which they would put an idol, you’re permitted to benefit from them, even though an idol was placed upon them, because what they would do is have these pedestals across the route that a king was supposed to take, and they would put idols on them on his journey for him to get out and bow down to them as he passed. So the Mishnah is telling us that those pedestals they put the idols on were not prohibited to benefit from. Why? Because they set up these idols on the pedestals only when the king actually passed by. Why? Because those pedestals were not used as permanent places for idol worship. They were only there temporarily when the king traveled, and sometimes the king would actually even take a different road, and he wouldn’t even pass these places. Therefore, the pedestals are not considered to be permanent places of Avodah Zarah (idol worship), and therefore they’re only temporary. We learned earlier on in the Masechet that when something is only temporary, it does not become prohibited to benefit from. But if pedestals were obviously used in a permanent fashion, then those pedestals would not even become prohibited.