Commentary for Avodah Zarah 4:6
עֲבוֹדָה זָרָה שֶׁהִנִּיחוּהָ עוֹבְדֶיהָ בִּשְׁעַת שָׁלוֹם, מֻתֶּרֶת. בִּשְׁעַת מִלְחָמָה, אֲסוּרָה. בִּימוֹסְיָאוֹת שֶׁל מְלָכִים, הֲרֵי אֵלּוּ מֻתָּרוֹת, מִפְּנֵי שֶׁמַּעֲמִידִין אוֹתָם בְּשָׁעָה שֶׁהַמְּלָכִים עוֹבְרִים:
An idolatry left behind by its worshipers — If [they left it behind] in a time of peace, it is permitted [Since they went of their own volition and did not take it with them, (it is a sign that) they nullified it]; in a time of war, it is forbidden. The bimusioth of kings [hewn stones fixed on the road for the king as pedestals for idolatry, so that when he passes by there he may bow down to it] are permitted because they are placed there when the kings pass by. The Gemara explains: "Because they place it down." That is, they are not fixed there for all times, but only when the kings pass by. And there are times when the kings pass over different roads and are not concerned for them. Therefore, they are not considered "appurtenances of idolatry."]
Bartenura on Mishnah Avodah Zarah
English Explanation of Mishnah Avodah Zarah
in time of war it is prohibited.
Pedestals of kings are permitted because they set them up at the time the kings pass by.
Mishnah six discusses idols which have been abandoned by those who previously worshipped them. The question is, can we assume that the worshipper has annulled the idol by abandoning it and it is therefore permitted to the Jew.
Section one: If an idolater abandoned his idol in time of peace the idol is permitted since we can assume that the idolater has no intention of returning to worship the idol. For instance if Maximus the idolater decides to move from Jaffa to Caesarea and he leaves his idols behind, he has shown that he doesn’t intend to worship them anymore. However, if Maximus the idolater flees his home during a war and in distress leaves his idols behind, he may intend to return and worship them when the war is over. Therefore they are not considered to be annulled.
Section two: Pedestals which were set up on the sides of roads to place upon them idols when kings pass by are not forbidden to Jews, since they are only temporarily used by the kings. During other times, when normal people pass them by, they do not worship these pedestals.
The mishnah connects these two issues because the pedestals are like idols that have been abandoned by their owners. When the kings are not there these idols are “abandoned”.