Avodah Zarah 42B

והא שיפויין, דעיקר עבודה זרה קיימת, וקתני: לצרכה ⁠— היא אסורה, ושיפוייה מותרין!

The Talmud asks: But consider the case of shavings, where the main object of idol worship still exists, and nevertheless it is taught in the baraita cited earlier that if a non-Jew shaved an idol down for its own sake, the idol is forbidden, but its shavings are permitted. Here too, in the case of the fallen leaves of a tree that is worshipped as an idol, it should be permitted to derive benefit from them.

רב הונא בריה דרב יהושע אמר: לפי שאין עבודה זרה בטלה דרך גדילתה.

Rav Huna, son of Rav Yehoshua, says: The reason the leaves are not permitted is because the status of an object of idol worship cannot be revoked by its natural manner of growth. Since the falling of leaves is a natural phenomenon, their detachment from the tree does not effect a revocation of their status as objects of idol worship.

איתיביה רבי שמעון בן לקיש לרבי יוחנן: קן שבראש האילן של הקדש ⁠— לא נהנין ולא מועלין, בראשה של אשרה ⁠— יתיז בקנה.

R' Shimon ben Lakish raised an objection to the opinion of R' Yoḥanan from a Mishnah (Me’ila 13b): With regard to a bird’s nest at the top of a tree that belongs to the Temple treasury, one may not derive benefit from it ab initio, but if one derived benefit from it, he is not liable for misuse of property consecrated to the Temple. With regard to a nest that is at the top of a tree used as part of idolatrous rites [ashera], although one may not climb the tree, as that would be benefiting from an object of idol worship, he may knock the nest off with a pole and benefit from it by using it for firewood and the like.