A Believer (Mu’min) might have propensity toward any (and all) faults, except Betrayal and Lying, said the Prophet peace be upon him

فيض القدير، شرح الجامع الصغير – للإمامِ المناوي
الجزء الخامس >> [تابع حرف الكاف]

[ص 19] 6300 – (كل خلة يطبع عليها المؤمن) أي يمكن أن يطبع عليها (إلا الخيانة والكذب) فلا يطبع عليهما وإنما يحصل له ذلك بالتطبع ولهذا صح سلب الإيمان عنه في قوله “لا يزني الزاني حين يزني وهو مؤمن” ولا معارضة بين استثناء الخصلتين هنا وخبر من كن فيه كان منافقاً خالصاً ومن كان فيه خصلة منهن كان فيه خصلة من النفاق من إذا أؤتمن خان وإذا وعد أخلف وإذا حدث كذب لأن خلف الوعد داخل في الكذب والفجور من لوازم الخيانة.
(ع عن سعد) بن أبي وقاص رمز المصنف لحسنه وأورده ابن الجوزي في الواهيات وقال: فيه علي بن هاشم مجروح وقال الدارقطني: وقفه على سعد أشبه بالصواب وقال الذهبي في الكبائر: روي بإسنادين ضعيفين اهـ.

A believer might drink, or fornicate or steal or gamble, but a believer never lies and never betrays the trust.

I like to give you real and unconventional examples, to raise awareness of our modern times, how we tend to sanitize our daily lives from obvious crimes for the sake of comfort and prosperity:

To take an oath of allegiance mentioning Allah’s name, to be a citizen of a nation e.g. USA or Canada, to defend and be loyal to the nation and yet in one’s heart consider this as an invalid oath just to gain materially. Such is a lie, and the person who takes such allegiance in falsehood far away from state of Iman (Faith).

To actively gain materially from a war based economy e.g. USA , with full knowledge of that one’s brothers and sisters are slaughtered in millions overseas, is betrayal and far from the state of Iman (Faith).

To encourage Muslim youth to join senseless slaughter in far away lands, knowingly sending them to certain death, while enjoying life with one’s family in security and prosperity, is both lying and betrayal and far from the state of Iman (Faith).

A Muslim youth embarking upon violent activities under the banner of Jihad, without taking the parents’ permission, is both lying and betrayal and indeed far away from the state of Iman (Faith).

If the Jihad is at the doorstep of any of you (Dara: Jihad that might be violent) do not exit except by the permission of the parents, said the Prophet.

A man came to the Prophet to ask permission for Jihad (Dara: might have involved violence) and the Prophet asked him: Are your parents living? the man replied affirmative, then Prophet said: Mention it to them (i.e. ask for permission to leave)