The Meaning of Deceit
Khida` linguistically: khada`ahu yakhda`uh khad`a wa khida`a is used to mean to trick someone, wishing evil for them whence they do not expect. Khad` is showing other than what is concealed.  al-Sihah, al-Jawhari (1/165); Lisan al-`Arab, Ibn Manzur (8/63).
Khida` technically: is trickery and slyness by manifesting goodness and hiding other than it to fulfill the trickster’s goal.  Ighathat al-LahfanLahafan, Ibn al-Qayyim (1/340). The Difference between Deceit, Delusion (Ghurur), and Conspiracy (Kayd)  al-Furuq al-Lughawiyyah, al-`Askari (p. 258, 383).
Delusion is a supposition which carries man into doing what is harmful. Deceit is to hide what is right from another to make them fall into harm. Conspiracy is solely after much deliberation, contemplation, and thorough thought. It is said that conspiring is to cause harm to others forcefully, whilst deception is to do so without force, but rather by convincing the other that harm is benefit. Among its forms are deceit in dealing with others. Deceit is manifesting other than what is hidden to gain benefit or cause harm, and is not necessarily after thorough contemplation or thought.Dispraise of Deceit in the Qur’an and Sunnah
❖ Allah, exalted, says: “They seek to deceive Allah and the believers, yet they only deceive themselves, but they fail to perceive it.” al-Baqarah: 9.
❖ He, exalted, also says, addressing His Messenger and the believers so that they may be wary of their enemy’s deceit: “If they intend to deceive you, Allah is enough for you. It is He who gave you victory through His help and the believers.” al-Anfal: 62.
❖ Abu Hurayrah, Allah be pleased with him, said: “The Messenger of Allah ﷺ said: ‘The believer is simple and magnanimous, while the wicked is deceitful and ignoble.”  Reported by Abu Dawud (4790), al-Tirmidhi (1964), and Ahmad (9170) from the narration of Abu Hurayrah, Allah be pleased with him. Quotes of the Predecessors and Scholars on Dispraising Deceit
❖ Ayyub, Allah have mercy upon him, said: “They deceive Allah as if they are deceiving a human being. If they are upfront with the matter, it would be preferable.”  Reported hung by al-Bukhari in the command form before the narration with number (6964). Ibn Hajar said in Taghliq al-Ta`liq (5/264): “Waki` said in his Musannaf: ‘Sufyan ibn `Uyaynah narrated this from Ayyub.’”
❖ Ibn Abi Awfa said: “The deceitful haggler is a betraying consumer of usury. This is evil deception and it is impermissible.”  Reported hung by al-Bukhari in the command form before the narration with number (2142). Categories of Deceit
Deception is of two types: one praiseworthy and the other blameworthy. If it is rightful, it is the former, and if wrongful the latter. Among the forms of praiseworthy deceit is his statement ﷺ: “War is deception.”  Reported by al-Bukhari (3030) and Muslim (1739). Among the blameworthy type is him saying ﷺ, from the narration of `Iyad ibn Himar, Allah be pleased with him, that is reported by Muslim in his Sahih: “The inhabitants of the Fire are five types of people…He then mentioned among them the one who deceives you day and night against your family and wealth.” He, exalted, says in regard to evil deception: “They seek to deceive Allah and the believers, yet they only deceive themselves, but they fail to perceive it.” al-Baqarah: 9. He, exalted, also says: “If they intend to deceive you, Allah is enough for you.” al-Anfal: 62.Forms of Blameworthy Deceit
The hypocrites’ deception with the people, manifesting Islam whilst hiding disbelief. Deceit in financial transactions, like buying and selling. The masses deceiving their rulers by flattering them and praising them for traits they do not possess. The ruler deceiving his subjects by oppressing them and not fulfilling their rights. The deception of the pretentious. They resemble the hypocrites in their showing off to the people. Deceiving a friend by harming them. Deceiving workers by not giving them their agreed-upon wages, or giving them responsibilities that are greater than their capacity. Means to Desisting from Deception
Sincerity to Allah in everything one does. Spiritual nurturing upon virtuous morals and adhering to the Divine Law’s rulings. Having trust in Allah and sensing His watchfulness. Contentment with one’s provision. Accompanying the righteous. Punishing the deceitful to deter him from his deceit. Deceit in Proverbs and Poetry
❖ They say: “So-and-so tames (yuqarridu) so-and-so.” This is said if one deceives another kindly. Its origin comes from the following phenomenon: a man approaches camels in the night with the intention to ride one of them. He fears that the one he approaches is frightened, so he calms it by stroking it and picking its ticks - a known parasite on camels - until it is tranquil towards it, and then he muzzles it.  al-Amthal, Ibn Salam (1/12); Taj al-`Arus, al-Zabidi (9/27).
❖ They say: “He has left deceit (khida`), he who takes off his mask (qina`).”  al-`Iqd al-Farid, Ibn `Abd Rabbih (7/119).
❖ They also say: “More deceitful than a dabb lizard.”  al-Sihah, al-Jawhari (1/165).
❖ The poet said:
“Say to him, the one whose camouflage baffles me -
I know not whether he is an advisor or a sly foe -:
‘I find me bewildered at what you describe me with:
With one hand you batter me, and the other heals me.
You backbite me among some, and then praise me
With others - all this reaches me from your behalf.
These are two irreconcilable matters, too contrasting.
Hold your tongue from both my dispraise and adulation!’”  al-Sadaqah wa al-Sadiq, Abu Hiyyan al-Tawhidi (p. 198).