Included in this subject is the hadith of Hatib Ibn Abi Balta’ah (1) (who sent a secret letter telling of the Muslims military plans to his relatives in Mecca in hopes that they would not get hurt), 'Umar (Allah be well pleased with him) wanted to kill him for what he had done, but the Prophet (pbuh) forbade 'Umar to, as Hatib had fought at Badr (and by accepting Hatib's excuse, left nothing for any Muslim to criticize.3

If someone's spying entails undermining Islam and its people, or the killing of captives, enslavement, or plundering of the Muslims, or anything of the like, then he is one of those who strive for corruption in the land, destroying tillage and offspring, and he is subject to death, and deserves the torment (of Hell- Fire), may Allah save us from it, Anyone who spies necessarily knows that if ordinary talebearing is a major sin, spy's carrying information is far more abominable and heinous, May Allah save us from that for He is the Ever-Clement?