(When a single disaster smites you), in reference to when the Muslims suffered seventy fatalities during the battle of Uhud,
قَدْ أَصَبْتُمْ مِّثْلَيْهَا
(although you smote (your enemies) with one twice as great,) during Badr, when the Muslims killed seventy Mushriks and captured seventy others,
قُلْتُمْ أَنَّى هَـذَا
(you say: "From where does this come to us") why did this defeat happen to us
قُلْ هُوَ مِنْ عِندِ أَنْفُسِكُمْ
(Say, "It is from yourselves.") Ibn Abi Hatim recorded that `Umar bin Al-Khattab said, "When Uhud occurred, a year after Badr, Muslims were punished for taking ransom from the disbelievers at Badr in return for releasing the Mushriks whom they captured in that battle. Thus, they suffered the loss of seventy fatalities and the Companions of the Messenger of Allah gave flight and abandoned him. The Messenger suffered a broken tooth, the helmet was smashed on his head and blood flowed onto his face. Allah then revealed,
Immediately later, in verse 166, the words fa bi idhnillahi: فَبِإِذْنِ اللَّـه indicate that whatever happened there was with the leave and will of Allah Almighty operating behind which are many wise divine arrangements, some of them having been explained earlier. One such wise arrangement is that Allah will 'see' His true believers, and the hypocrites too, that is, the sincerity of Muslims and the hypocrisy of the hypocrites will become so clear that everybody could see it for himself. Here, the reference to Allah's knowing or seeing means seeing in the perspective of our own sense-experience in the mortal world. Otherwise, as far as Allah is concerned, He knows and sees everything, all the time. So, the wise arrangement became all the more clear when, at the time of the trial, the hypocrites bowed out of the harm's way while true Muslims stood undaunted' in the middle of the battle front.
Tazkirul Quran
Maulana Wahiduddin KhanOn ayahs 164–166
The example set by the Prophet throughout his life must be followed by all reformers till Doomsday. For the task of reformation to be successful, it is essential that the targeted people should feel as if the reformer is one of themselves in every respect. His language, his style of speaking, his style of living— all should be familiar to them. No such feelings should be created between him and his addressee that may lead, in one way or another, to the latter becoming distanced from him, or to the addressee and the reformer becoming rivals. The first task to be performed among the people is to foster in them the ability to read the signs of God spread everywhere within and without their own selves. God’s signs should become part of their very mental make-up. The second task is to purify people. This end is achieved by the reformer speaking to them in person and giving them the opportunity to spend time in his company. The message can, of course, be put across through general discourses and writing, but this would only be in principle; whereas by resorting to individual communication the message can be conveyed in a more precise and detailed way. Then there is the question of the personality of the dayee, which should always lend weight to the message. Individual meetings thus serve the purpose of the purification of the addressees, or madu‘. The third task is to introduce to the madu‘ the shariah—the book of guidance on how life should be led in this world. The fourth task is to impart wisdom, that is, to unveil the secrets of religion and to highlight the truths hidden between the lines.