The ruling on killing the spy.

The Shaykh : Accordingly, if we find a Muslim spy who informs the disbelievers of our news, it is obligatory to kill him. Even if he says, "I bear witness that there is no god but Allah and that Muhammad is the Messenger of Allah," he must be killed without exception. This is because the Messenger (peace and blessings be upon him) did not prohibit killing him except because he was from the people of Badr, and this is a distinction that has not been attained to this day, nor will it be attained until the Day of Resurrection. The scholars (may Allah have mercy on them) used this hadith as evidence that the spy is killed, whether he is a Muslim or a disbeliever, in all cases, because he leaks our news to our enemies. And success is from Allah.