The Meaning of Spying
Tajassus linguistically: is taken from jassa al-khabar to mean searched and looked for some news. Tajassus is searching for the hidden parts of things, mainly used in an evil sense. al-jasus (the spy) is a person who spies for matters then returns with their news. He is the possessor of evil secrets, whereas al-namus (the confidant) is the possessor of good secrets.  See: Tahdhib al-Lughah, al-Azhari (10/242); Lian al-`Arab, Ibn Manzur (6/38); Taj al-`Arus; al-Zabidi (15/499).
Tajassus technically: is searching for private matters and faults, exposing what the people have concealed.  al-Tafsir al-Munir, al-Zuhayli (26/247). The Difference between Spying and Sensing (Tahassus)  al-Furuq al-Lughawiyyah, al-`Askari (p. 118); Tanbih al-Ghafilin, Ibn al-Nahhas (p. 45-46).
Sensing (tahassus with the harsh ha) is seeking a thing through the senses. Spying (tajassus with a jim) is similar. It is said they are of the same meaning. It has also been said that spying is searching for women’s privacies, whereas sensing is listening to people's speech. It is narrated that Ibn `Abbas, Allah be pleased with them both, was asked about the difference between them so said: “They are not far from one another: sensing is to do with what is good, whereas spying is with regards to evil.” The difference has also been described as sensing being firsthand reception of news, whereas spying is secondhand. It is also said that sensing is seeking another’s news and searching for them out of pity, to give advice, and out of precaution, such that one is contented at the other’s wellness - at least one would aid the other if they seem unwell, with goodwill, care, and support. This is in contrast to spying where one seeks others’ news and states to uncover what they would dislike to be known - one extracts them with one’s searching to expose the other's privacy and defect.Dispraise of Spying and its Prohibition in the Qur’an and Sunnah
❖ Allah, exalted, says: “Believers, avoid making too many assumptions - some assumptions are sinful - and do not spy on one another or speak ill of people behind their backs: would any of you like to eat the flesh of your dead brother? No, you would hate it. So be mindful of Allah: Allah is ever relenting, most merciful.” al-Hujurat: 12.
❖ He, exalted, also says when describing the hypocrites’ traits: “Had they gone forth with you, they would have only added to your trouble, and would have run about in your midst seeking to stir up sedition among you, whereas there are among you some who are prone to lend ears to them. Allah knows well the wrong-doers.” al-Tawbah: 47.
❖ Abu Hurayrah, Allah be pleased with him, narrated that the Prophet ﷺ said: “Beware of supposition, for it is the most false of speech. Do not stalk, spy on, deceit, envy, hate, nor forsake one another. Be, slaves of Allah, brothers.”  Reported by al-Bukhari (6064) and Muslim (2563).
❖ Abu Barzah al-Aslami, Allah be pleased with him, said: “Allah’s Messenger ﷺ said: ‘Assembly of those who proclaimed faith with their tongues but it is yet to enter their hearts, do not backbite the Muslims nor follow up their private matters. Whoever does so, Allah will follow up on his privacy. Whomsoever Allah follows his privacy, he will expose him in his home.”  Reported by Abu Dawud (4880) and Ahmad (19776). al-`Iraqi deemed its chain good in Takhrij al-Ihya’ (3/175). al-Albani said in Sahih Sunan Abi Dawud (4880): “It is sound, authentic.” Quotes of the Predecessors and Scholars on Dispraising Spying
❖ Abu Qilabah narrates that `Umar ibn al-Khattab, Allah be pleased with him, was informed that “Abu Mihjan al-Thaqafi drank alcohol with his friends in his home.” `Umar went forth until he entered upon him. There was only one other man with him. Abu Mihjan said: “Commander of the Faithful, this is not lawful for you. Allah forbade you from spying.” `Umar said: “What do you say of this?” Zayd ibn Thabit and `Abdullah ibn al-Arqam both said: “He is right, Commander of the Faithful. This is spying.” `Umar went and left him.”  Reported by al-Tha`labi in al-Kashf wa al-Bayan (9/83).
❖ Qatadah said in interpretation of His statement: “Do not spy on one another”: “Do you know what spying is? It is that you follow your brother’s faults to find out his secrets.”  Jami` al-Bayan, al-Tabari (22/304). Impacts of Prohibited Spying  al-Tahrir wa al-Tanwir, Muhammad al-Tahir ibn `Ashur (26/253-254).
Spying is a manifestation of ill faith and one of its consequences. It is the result of an evil, blameworthy trait which the pure faith rejects. It is a manifestation of weak faith and religiosity, and a lack of godly awareness. This is from a religious perspective. As for the moral, spiritual perspective, then it is a sign of the self’s lowliness and depravity, its lack of aspiration, and it being busy with banal, trivial matters as opposed to the most critical and lofty ones. It is a way for amicable ties to be broken, relations to become void, dear ones having enmity against each other, and brothers splitting up. Spying leads to a corrupt life, making it rife with doubts and fears such that one never feels secure with his privacy that it may be breached or become public to the masses. One ends up in a never-ending cycle of doubt and uncertainty. Spying is a path to hatred and an instigator of vengeance. If one becomes aware that some person is exerting himself to expose one’s privacy and scandalise one’s personal affairs, he will in turn vie to respond in kind. Spying is a means to spread debauchery and vice among Muslims, since the former facilitates the exposure of otherwise hidden lewdness and obscenity. It is a clear indicator of an evil conscience and deeply imbedded hypocrisy in the heart, and that its possessor is far from faith even if he claims it, short of piety even if he endows himself with its clothing. Its possessor is warned against scandalous humiliation and exposure even if he is in the safety of his own home. It suffices as an evil testimony for spying that he who does it incurs Allah’s wrath and His painful punishment in the next life. In this worldly life, he is hated and disliked by the people - they constantly doubt him, never fully being relaxed in his presence. Forms of Spying
● Forms of Unlegislated Spying
❖ Spying on Muslims in their homes, seeking to expose their privacies.
❖ Breaking into homes and private places to catch their inhabitants in the act of sin. This is unlawful and unequivocally rejected by the Law.
❖ Probing and searching for sins and faults which have been committed in the past, spying on those who undertook them to know them.
❖ One listening in on a group conversation while they dislike him doing that.
❖ Spying on the Muslims for the benefit of the enemies of the religion.
● Forms of Legislated Spying
❖ Spying on the enemies of the Ummah to find out their numbers and preparation.
❖ Following dangerous and suspicious criminals.
❖ The ruler checking up on the state of his people, so that he is aware of the oppressed and the needy, securing their rights, as they are a trust the ruler is bound to serve.  `Uqubat al-I`dam, Muhammad ibn Sa`d al-Ghamidi (p. 469). Causes of Unlegislated Spying
Pure curiosity. Intent to harm and expose. Ill faith. Vengeance and treating others with the like: that the spied upon spies back on whoever is spying upon them in retaliation. Material gain: that the spy is financially motivated through some institution. Means to Desisting from Spying
That one is watchful of Allah, blessed and exalted, at all times and with all things, fearing His painful punishment and the power of his vengeance. That one leaves off his curiosity and his love of uncovering others’ personal matters. That one instills within himself desire for the Muslims’ unity and their coming together, fearing that they become split and fragmented through severed ties. That one contemplates the evil consequences of this quality in the Qur’an, Sunnah, and statements of the Predecessors. In this is a strong repellent from engaging it. That he realises what he is doing is harmful to Muslims by all standards, and that harming them is legally impermissible. That the one spying fears that he himself is exposed as warned by the Messenger of Allah ﷺ, that those who follow people’s privacies will be exposed even if in the depths of their homes. Spying in Poetry
The poet said:
“Do not look for what the people had hid of evil
Such that they uncover the secrets of your evil.
Mention their good traits if they are mentioned
And shame not another for a defect you have.”  Rawdat al-`Uqala’, Ibn Hibban al-Busti (p. 128).