After making all this clear...
After making all this clear, now Allah explains the immediate cause of that disaster according to the law of causality. He tells them that debacle was caused by their disobedience which they committed on that day: the disobedience of the archers when they left their position, and then the disobedience of all those who fled away from the battlefield. In short, the disaster took place because they disobeyed the Messenger, their Commander, and showed lack of courage and disputed among themselves.
All this led to their retreat according to the law of nature and custom. The verse's meaning is therefore as follows: Do you know how this misfortune befell you? Was it not a misfortune that you had previously inflicted twice as much on your enemies, the unbelievers? This time the disaster was brought on you by your own selves.
It were you who undermined the means of victory with your own hands; it were you who did not follow the clear order of your Commander, fell into temptation and disputed one with the other.
The clause, "while you had certainly afflicted (the unbelievers) with twice as much", prompts them to compare their losses in Uhud (martyrdom of seventy believers) with those suffered by the unbelievers in Badr when they had suffered twice as many casualties — as seventy of the unbelievers were slain and seventy taken prisoners. This description is intended to soothe the believers' feelings, making the calamity look less devastating.
After all, they have suffered only half of that, which they had inflicted on their enemies; so they should not grieve, should not be distressed. Some people have explained it differently. According to them the clause, "It is from your own selves", means that you yourselves had opted for this misfortune. It happened like this: They had chosen to release the prisoners of Badr in exchange for ransom.
But the initial order was to kill them; and they were warned that if they accepted the ransom, a similar number from their side would be killed next year; but they said: "We agree to this condition. We shall take the ransom and enjoy its benefits; and if one of us is killed later on, he shall be a martyr. " The ending clause of this verse (surely Allah has power over all things) supports, or rather proves, this latter explanation; as this clause does not connect properly with the former meaning.
We shall quote in the next "Traditions" ahadith from the Imams of the Ahlu 'I-bayts (a.s.) regarding this topic.