Reason behind revealing This Ayah, and the prohibition of Betrayal

The Two Sahihs mention the story of Hatib bin Abi Balta`ah. In the year of the victory of Makkah he wrote to the Quraysh alerting them that the Messenger of Allah ﷺ intended to march towards them. Allah informed His Messenger of this, and he sent a Companion to retrieve the letter that Hatib sent, and then he summoned him. He admitted to what he did. `Umar bin Al-Khattab stood up and said, "O Allah's Messenger! Should I cut off his head, for he has betrayed Allah, His Messenger and the believers" The Prophet said,

«دَعْهُ فَإِنَّهُ قَدْ شَهِدَ بَدْرًا، وَمَا يُدْرِيكَ لَعَلَّ اللهَ اطَّلَعَ عَلَى أَهْلِ بَدْرٍ فَقَالَ: اعْمَلُوا مَا شِئْتُمْ فَقَدْ غَفَرْتُ لَكُم»

وَاعْلَمُوا أَنَّمَا أَمْوَالُكُمْ وَأَوْلَادُكُمْ فِتْنَةٌ وَأَنَّ اللَّـهَ عِندَهُ أَجْرٌ‌ عَظِيمٌ ﴿28﴾(And be aware that your wealth and your children are but a trial and that with Allah there is a great reward).

The word: فِتنَہ (fitnah) used here carries the sense of 'trial' as well as that of 'punishment.' Then, such things as become the cause of punishment are also referred to as fitnah.' In different verses of the Qur'an, 'fitnah' has been used to carry these three meanings. At this place, there is room for all three. There are occasions when one's own property and children become a can of troubles for him and that they would push him into negligence and disobedience and become the very cause of punishment right here in this world is all too obvious. Firstly, the sense could be that Allah aims to put you to test through your property and children for these are His blessings. Now, you prove whether you become grateful and obedient after having received these, or that you choose to be ungrateful and disobedient. Also possible is the second, even the third meaning, that is, should you become all engrossed in your love for your property and children and bring upon yourself the displeasure of Allah, then, these very children and property will become your punishment. There are occasions within this mortal world when one is engulfed into all sorts of hardships because of property and children and he starts experiencing the heat of punishment right here. Even if the case be otherwise, it stands settled that the property which was acquired or spent by ways counter to the injunctions of Allah Ta` ala will itself become, in the Hereafter, the active agent of punishment through snakes, scorpions and brandings by fire - as stated clearly in several verses of the Qur'an and numerous narrations of the Hadith. Finally, the third meaning is that these things become the cause of punishment. As pointed out a little earlier, it is quite evident that once these things become the cause of heedlessness towards and disobedience to Allah Ta` ala and His injunctions, they automatically become the cause of punishment. At the end of the verse (28), it was said: وَأَنَّ اللَّـهَ عِندَهُ أَجْرٌ‌ عَظِيمٌ (and that with Allah there is a great reward). In other words, one should understand clearly that for a person who is not all-subdued by his love for property and children while doing his duty of being obedient to the commands of Allah and His Rasul, there is a great reward for him with Allah.