Baba Kama 90a - חמץ נוקשה שעבר עליו הפסח ודבר הגורם לממון

The Ketzos HaChoshen (386:7) raises a question: If one destroys his friends chometz on pesach, he is clearly not liable for the damages since both on pesach and after pesach that chometz will be prohibited from deriving any benefit from. However, if one destroys "chometz nuksheh" of his friend, will he be liable to pay for the damages? The status of chometz nuksheh is that one is allowed to own it through pesach with the intent of using it after pesach, but during pesach one is not allowed to derive any benefit from it. The concept behind the practical scenario is whether one is liable for damages on an object which at the moment is not usable in any way, but has value in the sense that at a later time it will be usable. The ketzos writes that this would seem to be categorized as a דבר הגורם לממון, similar to what the gemara in pesachim 29a describes in the context of benefiting from hekdesh chometz during pesach. Hekdesh chometz will also be permitted after pesach, but during pesach one is not allowed to derive any benefit from it. Will this constitute a violation of me'ila - the gemara makes this dependent on the rule of davar ha'gorem l'mamon. Since we pasken that דבר הגורם לממון לאו כממון דמי, he is patur.

The ketzos raises a problem from our gemara, where the slave is sold and the original owner retains rights of use for the next 30 days, and the slave will then be fully owned by the buyer. R' Meir holds that the rights to use the eved is like a kinyan ha'guf, so that the din יום או יומיים to exempt the master for killing the eved applies to the original owner. The ketzos asks that since r' meir agrees with r' shimon that davar ha'gorem l'mamon is k'mamon (baba kama 71b), shouldn't r' meir hold that the ownership of the buyer is significant since after 30 days it will belong entirely to him? From this the ketzos is mechadesh that the concept of דבר הגורם לממון does not decide ownership, it is just a method of assessing responsibility for damage....

Many achronim take issue with the assumption of the ketzos that something which has no value now because it cannot be used but will have real value later is considered to merely be a davar ha'gorem l'mamaon. Perhaps hekdesh is different since its entire value is based on the ability to redeem it, therefore on pesach when no one will consider redeeming it, it has zero value. But something which can not be used temporarily such as chometz nuksheh, but will be usable at a later date, is considered to have real value now and the damager would be responsible.