פירוש על קידושין 46:6

The Talmud presents a possible explanation of the dispute in the mishnah. R. Meir would hold that a slave cannot acquire property independent of his master (nor a wife independent of her husband). The second the money goes into his hand, it belongs to his master. Therefore, the slave cannot give the money to free himself. The other rabbis say that a slave can acquire money separate from his master. So if others give him money to redeem himself, he can take the money and redeem himself.