(Mishnah): If an idol was abandoned by its worshipers - if it occurred at a time of peace, it is permitted; if at a time of war, it is prohibited (as they might be intending to return for it, rather than have annulled it).

Platforms of kings (upon which idols were placed) are permitted, because they are set up for when the kings pass by.

(Gemara) (Beraisa): If the nations left an idol during the war of Yehoshua, sometimes it is prohibited and sometimes it is permitted. And similarly for the war of David HaMelech.

When were they prohibited from the war of Yehoshua - as the pasuk states (Devarim 20:17), "Rather, you shall utterly destroy them"; but since the nations intended triumphing against Bnei Yisrael, they did not annul their idols. The idols that are permitted belong to those idolaters who survived the wars and could have returned to take the idols but did not.

The idols from the war of David that were permitted, were those annulled by Itai the Gittite. Those that were prohibited and that he therefore destroyed were the ones not annulled by Itai the Gittite.

(Mishnah): They asked the Sages in Rome, "If He (Hash-m) does not want idolatry, why doesn't He annul it?

(Sages to the Romans): He would annul things that they worship that the world does not need; but since they worship the sun, the moon, the stars, the constellations, the mountains and the hills, should He destroy the world because of the fools?

(Romans to the Sages): If so, let Him destroy anything that they worship that the world does not need and keep anything that they worship that the world needs?

(Sages to the Romans): If He would do that, he would give strength to those that worship the sun and moon etc. as they would say that these things are certainly gods as He did not (and could not) destroy them.

(Gemara - Beraisa): It should be that if one stole seeds and planted them, they should never grow; and if one was adulterous with a married woman, she should not give birth to a Mamzer. But Hash-m allowed the world to follow its natural course and in the future, the fools who sinned will give a reckoning.

(R. Zeira): If the pasuk would have said (Tehillim 115:8), "like them will be those that worship them" (rather than "like them will be those that make them"), one could ask - will those that worship the sun shine like the sun and those that worship the moon shine like the moon? Therefore, the pasuk states that "like them will be those that make them" - meaning those that make images like the sun and moon.

(R. Mana): If it would have written, "like them will be those that worship them", it would not have been a question, as the pasuk states (Yishayah 24:23), "And the moon shall be ashamed and the sun shall be abashed" (and the idolaters will be the same).