פירוש על קידושין 45:10

Rava offers a different reason for why R. Meir holds that a slave can be set free by money given by others but not by a document accepted by others. The slave goes free when his master receives the money. It is not that others are causing him disadvantage. But if the slave goes free by document he goes free when the others accept the document. Therefore, they are causing him detriment, and one may not cause detriment to another without his consent.