Is it permissible for a Muslim doctor to sell a dog owned by a non-Muslim, in order to recover money he previously paid for it as the price of the dog, after its owner allowed him to do so?

It is not permissible to sell a dog, even if it is one that is permissible to keep, such as a hunting dog, because the Prophet, peace and blessings be upon him, said: "The Prophet, peace and blessings be upon him, forbade the price of a dog," and his saying: "The price of a dog is not lawful." The majority of scholars have ruled that selling a dog is forbidden and that its price is invalid. Therefore, the doctor should not give the price of the dog to its owner, as the dog has no legal value.

The Chinese man must return the money to the doctor, and he himself should sell the dog. It is not permissible for the doctor to take the dog in exchange for the money, nor to sell it to recover his money, because its sale is forbidden. There is no blame on the doctor for taking the money, even if it is from the price of a forbidden dog sale, because the sale of a dog by a disbeliever is permissible according to some jurists, just as the sale of a hunting or guard dog is also permissible.

Shaykh al-Islam Ibn Taymiyyah said: "Whatever is received by interpretation, it is permissible for a Muslim to buy it from the one who received it, even if the buyer believes that the contract is forbidden."