The Meaning of Betrayal
Khiyanah linguistically: is the antonym of trustworthiness. Betrayal is that one is entrusted but does not deliver.  al-Mufradat, al-Raghib (p. 305); Lisan al-`Arab, Ibn Manzur (13/144).
Khiyanah technically: is going against someone’s right by breaking a promise in secret. It encompasses all religious legal burdens. It is also described as domineering others with what one is entrusted over of wealth, privacy, or prohibitions; gaining ownership over what is given as a trust, denying those who entrusted one with them.  Tahdhib al-Akhlaq, al-Jahiz (31); Mura`at al-Mafatih, al-Mubarakfuri (8/229). The Difference between Betrayal, Thievery (Sariqah), and Hypocrisy (Nifaq)  al-Furuq al-Luhawiyyah, al-`Askari (p. 228); al-Mufradat, al-Raghib (p. 305).
The traitor is the one who takes what he is entrusted with. The thief is the one who secretly steals from another in any way. Not every thief is a traitor. The coercer (ghasib) is the one who is openly your foe and does not hide it. Cutting people off (qat`) is only in thievery, not betrayal nor coercion.
Betrayal and hypocrisy are one, except that the former is with regard to oaths and trusts, whereas the latter in regard to religion.Dispraise of Betrayal and Warning against it in the Qur’an and Sunnah
❖ Allah, exalted, says: “Allah will defend the believers; Allah does not love the unfaithful or the ungrateful.” al-Hajj: 38.
❖ He, sanctified, also says: “If you have reason to fear betrayal from a people, throw their treaty back to them on equal terms. Indeed, Allah does not like traitors.” al-Anfal: 58.
❖ `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 (34) and the wording is his, as well as Muslim (58). Quotes of the Predecessors and Scholars on Betrayal  Makarim al-Akhlaq, al-Khara’iti (71, 72, 155).
❖ Anas ibn Malik, Allah be pleased with him, said: “If there is betrayal in a household, its blessing disappears.”
❖ Khalid al-Raba`i said: “It used to be said: “Indeed, among those acts most worthy of not having their punishment delayed - or it should be hastened -: that a trust be betrayed, ties of kinship be severed, and kindness belied.”
❖ Mujahid said: “Cunning, trickery, and betrayal are in the Fire. They are not of the morals of the believer, cunning and betrayal.”Impacts and Harms of Betrayal
It incurs the wrath of Allah, honoured and majestic, over the slave. It is a fatal illness which, if it spreads in a person, rids him of his humanity, making him a beast that runs after its desires. It is a path to shame in this life and the Fire in the next. It is the worst thing man can conceal. The spread of betrayal in society is a sign of its waning. The spread of exploitation, bribery, fraud, and cheating. They are all forms of betrayal.  1-6 are from Nadrat al-Na`im by a group of authors (10/4479). Lack of trust between people in society. The breaking down of bonds of love and cooperation in society. It causes humiliation and abasement of its possessor. Forms of Betrayal  Akhlaq al-Munafiqin, Ya`qub al-Maliji (p. 84), with adaptation.
Betrayal to Allah and His Messenger. Betraying oneself by committing sins which only Allah can see, betraying Allah’s forbiddance of them. Betraying the people. This comes in different forms. In wealth it is to consume others’ wealth which one has been given as a trust. Divulging secrets is also betrayal, and so is betrayal in advice. Marital betrayal through theft and adultery. Ways in which Betrayal is Mentioned in the Qur’an
Betrayal appears in the Qur’an in five ways: Religion and religiosity: “Unfaithful to your trusts.” al-Anfal: 27. Wealth and blessings: “Do not be an advocate for those who betray trust.” al-Nisa’: 105 Law and Sunnah: “If they mean to betray you, they have betrayed Allah before.” al-Anfal: 71. Meaning, if they betrayed their trust in what is legally recommended, they have abandoned it before that in what is obligatory. Betrayal to mean adultery: “Allah does not guide the plan of betrayers.” Yusuf: 52. Meaning the fornicators. Betrayal as a Characteristic of the Jews
Allah has described the Jews as a betraying people, save some of them. He, exalted, has said addressing his Messenger ﷺ: “You will always find betrayal in all but a few of them.” al-Ma’idah: 13. This verse shows that betrayal is among the traits that manifest in Jews from time to time. Betrayal is their characteristic and habit, and their way in treating others.
Examples of their betrayal is their attempt to assassinate the Messenger ﷺ whilst he was in a peace treaty between them; also their alliance with the Combined Forces, and there was an agreement of safety between them and the Messenger.  al-Akhlaq al-Islamiyyah, `Abd al-Rahman al-Maydani (1/614). Betrayal in Poetry
The poet said:
“How befitting of who betrayal pleases as a trait
That he receives not but the calamities for events.
Troublesome matters still have their adversity
Reach the treacherous with oaths, their nullifier.”  Nihayat al-Arab fi Funun al-Adab, al-Nuwayri (3/364).