The Meaning of Treachery
Ghadr linguistically: is not upholding a thing, abandoning it. It is the opposite of loyalty to promises.  Taj al-`Arus, al-Zabidi (13/203).
Ghadr technically: is breaking oaths, not upholding a thing and abandoning it.  al-Tawqif `ala Muhimmat al-Ta`arif, al-Manawi (p. 250). The Difference between Treachery and Cunning (Makr)
Treachery is nullifying an oath that one had to fulfil. Cunning may be instigated with no prior pledge.  al-Furuq al-Lughawiyyah, al-`Askari (p. 508-509). Dispraise of Treachery and its Prohibition in the Qur’an and Sunnah
❖ Allah, exalted, says: “Fulfil any pledge you make in Allah’s name” al-Nahl: 91.
❖ Allah, exalted, also says: “Honour your pledges: you will be questioned about your pledges.” al-Isra’: 34.
❖ `Abdullah ibn Mas`ud, Allah be pleased with him, narrated that the Prophet ﷺ said: “There will be a flag for every perfidious person on the Day of Judgment, and it would be said: Here is the perfidy of so and so.”
❖ `Abdullah ibn `Amr, Allah be pleased with them both, narrated that the Prophet ﷺ said: “There are four traits: whoever has them all is a pure hypocrite. Whoever has one of them has a trait of hypocrisy until he rids himself of it. If he is entrusted, he betrays. If he speaks, he lies. If he takes an oath, he breaches it. If he falls out, he is wicked in his opposition.”  Reported by al-Bukhari (2459) and the wording is his, as well as Muslim (58). Quotes of the Predecessors and Scholars on Dispraising Treachery
❖ `Ali, Allah be pleased with him, said: “Treachery is cunning, and cunning is infidelity (kufr).”  Reported by al-Tabari in al-Tafsir (17/43).
❖ Ibn Hazm said: “Treachery cannot be borne by anyone, and no noble person can overlook it. It is the loathsome thing truly, and its deserter cannot be blamed in any way, shape, or form; be it out of forgetfulness or perseverance. Rather, blame may only be attributed to the one patient over it.”  Tawq al-Hamamah, Ibn Hazm (p. 253).
❖ al-Abhishi said: “How often did destiny trip the treacherous up into destruction, having constricted for himself expansive resources through the means of destructive ones, his treachery bounding him by a chain of humiliation he is unable to free himself from.”  al-Mustatraf, al-Abhishi (p. 216). Impacts and Harms of Treachery
Firstly: Upon Those who Enact it: Going astray and being misguided. Having a cruel heart. Compromising one’s dignity, decency, and gravitas, and allowing for the overpowerment of the enemy. Incurring the recompense of treachery. The Prophet ﷺ is absolved from the treacherous. The curse of Allah, the Angels, and all people befalling the treacherous. Being akin to the nature of the hypocrites. Exposure in front of the masses
Secondly: Upon the Islamic Mission Division and lack of unity. Lengthening the road, and increasing the burdensome load. Reasons for Falling into Treachery
Overburdening the self with what it cannot bear. Loving the disbelievers and allying with them. Befriending those known for treachery. Weak faith in Allah. Not contemplating the terrible consequences of treachery. Obsessively seeking the worldly life and its pleasures. One being raised in a family wherein the etiquettes of the Law are not kept to. Means to Desisting from Treachery
Nurturing sincere, strong faith in Allah, sanctified. That one does not overburden himself with what he cannot bear. Contemplating the terrible consequences of treachery on the individual as well as society. Reflecting over the Quranic verses that warn from treachery and disloyalty. Avoiding greed and obsession with the worldly life. Struggling against the self and nurturing it upon fidelity and truthfulness. Distancing oneself from bad company, and instead befriending the righteous. The Jews’ Treachery with Muslims
A treaty had been made between Allah’s Messenger ﷺ and the Jews after the Migration, and the Islamic State having strengthened and firmly founded. Thereafter, the Jews began to seek every opportunity for treachery against the Muslims. Banu Qaynuqa` were the first to betray when they uncovered the modesty of a Muslim woman in their souq, exposing her privacy. At that, the Messenger of Allah ﷺ besieged them with a Muslim army until he exiled them from Madinah and distanced them away to the Levant as a recompense for their treachery and betrayal with their covenant.
Banu al-Nadir followed suit in treachery. They planned to assassinate the Messenger of Allah ﷺ as he was sitting among them talking to them. They plotted to push a rock on him from the roof. Allah exposed their affair. He ﷺ besieged them with an army of the Muslims until they were also exiled to the Levant.
Finally, the greatest betrayal was from Banu Quraydhah on the day of the Combined Forces. That day, the Arab tribes among the polytheists gathered against the Muslims. When the Jews saw the constriction and compromise of the Muslims, they took this as an opportunity, announcing their unfaithfulness to their treaty, and joined the ranks of the idolaters. Allah exposed their slyness. Once the Combined Forces were defeated, Allah’s Messenger ﷺ attended to them, discipling them and making them an example for those to follow. The result was that their combatants were killed, and their offspring and wealth imprisoned.  Hiwar al-Hadarat, Musa Ibrahim al-Ibrahim (p. 193-193) citing from Ibn Hisham’s Sirah, with adaptation. Treachery in Adages, Proverbs, and Poetry  Muhadarat al-Udaba’ wa Muhawarat al-Shu`ara’, al-Raghib (1/351); Nihayat al-Arab fi Funun al-Adab, al-Nuwayri (3/364).
❖ “Loyalty is the trait of the magnanimous, and treachery is the deed of the ignoble.”
❖ “Do not wear your garments upon treachery.” It is said to encourage loyalty and praise it.
❖ They say: “The victor through treachery is parched, and he who breaches oaths is hated and deserted.”
❖ They say: “Treachery guarantees slipping up, and severs helping hands.”
❖ Thabit Qutnah said:
“Think not that treachery is firm; for
Your footstep may land on it then slip.”  Tarikh al-Tabari (6/459).