פירוש על עבודה זרה 83:15

Yes, I know that this source is a bit gross and quite strange as well. Why does the priest need to know if it is male or female? While it is true that there are different periods of purity and impurity for male or female births (see Leviticus 12), is this slave Jewish such that she would observe these laws? Why doesn’t the priest know that he should not look into the pit to see because that would make him impure? In any case, there seems to have definitely been a source of impurity placed into the pit. The doubt is over whether it is still there. And again, a doubt does seem to set aside a certainty.

The baraita quoted here discusses an idol that had pieces chipped off of it. If the idolater does this, then the status of the idol depends on the idolater’s intention. If he simply wants to use pieces of the stone for some other purpose, then he is no longer treating the idol with any sanctity. The idol has been annulled and a Jew can now make use of it. But if he chips a piece off to improve the idol, then the idol has not been annulled.
A Jew cannot annul idols. Therefore, it does not matter why he chipped off a piece.
But again, this is a difficulty against Resh Lakish. Why shouldn’t we consider this like an idol that broke on its own?
Resh Lakish can again solve this according to Rava’s statement. If a Jew chipped off a piece of the idol of a non-Jew, it should be annulled. But we consider it not to be annulled, lest the Jew come to possess the idol, and the idol of a Jew can never be annulled.