You see this really in the Tosephta on Sanhedrin. [Or at least that is where I first saw this idea.]
But stated clearly you have to see the Avi Ezri of Rav Shach in laws of idolatry 7:1.
So here I want to introduce that subject.
In tractate Avoda Zara 41:b. R.Yochanan said: an idol that broke by itself [e.g fell down in an earthquake] is still forbidden [to use, as e.g. to sell the pieces]] Reish Lakish said it is permitted. The Gemara asks from the mishna R Yose said a person can take an idol and crush it and throw it to the winds. The sages said "but then one might end up using the dust. and the verse says "So that nothing will stick to your hands from it". So why the gemara asks is this any different from an idol that broke by itself? (and we see the sages forbid it.)
The Gemara answers [for Reish Lakish] from Rava: it is a gezara (decree) because as he is crushing it he might pick it up and then he owns it an a Israeli can not nullify his own idol.
The Ritva asks the same question applies to R Yochanan since on page 43 we see he makes a distinction between when the idolater gives up from just the monetary worth of the idol or also from the prohibition.
To the Gemara, even R Yochanan would agree that if the idolater gave up on both, then the idol that broke by itself is permitted in use [as e.g. to sell the pieces].
The Ritva [a later rishon after Tosphot] answer the case of the idol that broke by itself is different for the idolater does not know yet that it broke. For it to be permitted there has to be knowledge that it broke and became worthless. [The point is that the question of the gemara on Reish Lakish would not apply to R Yochanan- Because to R Yochanan for the idol to be permitted in use the idolator has to be aware that it broke.]
Rav Shach in the Avi Ezri asks this same point ought to apply to Reish Lakish also. And his answer is the very point I made up above. To both Reish Lakish and R Yochanan an idol that can not save itself is not an idol. For the very essence of idolatry is the thought that people have of it that it can help. Onnce it is broken it automatically loses that category. But R Yochana requires at least an act of nullification.
[Even though it is still unclear to me where this idea comes from. I mean I have heard of requiring an act of "bitul" nullification but I am not sure where you see this here in R Yochanan. I am sure my learning partner David Bronson would be puzzling about this point maybe for weeks on end-unless an answer could be found.]
