Ibn 'Abbas narrated that 'Umar bin al-Khattab said

On the day of Badr, the Messenger of Allah (ﷺ) looked at his companions and they were three hundred and some, then he looked at the mushrikeen and saw that they were one thousand or more. The Prophet (ﷺ) of Allah(ﷺ) turned to face the qiblah, then he stretched forth his hands, wearing his upper and lower garment, and he said: “O Allah, where is Your promise to me? O Allah, accomplish for me what You have promised me! O Allah, if this small band of Muslims is destroyed, You will never be worshipped on earth.” He kept beseeching his Lord, calling out to Him, until his upper garment fell from his shoulders. Abu Bakr came to him, picked up his upper garment and put it on him. Then he embraced him from behind and said: O Prophet of Allah, this prayer of yours to your Lord will suffice, for He will accomplish for you what He has promised to you. Then Allah revealed the words: `(Remember) when you sought help of your Lord and He answered you (saying): ‘I will help you with a thousand of the angels each behind the other (following one another) in succession` [al Anfal 8:9). On that day when the armies met (in battle), Allah, may He be glorified and exalted, defeated the mushrikeen; seventy of their men were killed and seventy were taken captive. The Messenger of Allah (ﷺ) consulted Abu Bakr, 'Ali and 'Umar رضي الله عنهم (concerning the prisoners). Abu Bakr said: O Prophet of Allah, they are our cousins, kinsmen and brothers, I think that you should accept a ransom for them, which will strengthen us against the kuffar, and perhaps Allah will guide them to Islam and they will become a support to us. The Messenger of Allah (ﷺ) said: “What do you think, O son of al-Khattab?` I said: No, by Allah. I do not think as Abu Bakr thinks. I think that you should hand. So and so ­ a relative of ʼUmar's- ­ over to me so that I may strike his neck. You should hand ‘Aqeel over to ‘Ali so that he may strike his neck, and you should hand over So and so to Hamzah (his brother) so that he may strike his neck, so that Allah will know that we have no mercy in our hearts towards the mushrikeen; these are their prominent figures and leaders. But the Messenger of Allah (ﷺ) inclined towards the view of Abu Bakr, and he did not incline towards what I said, and accepted ransoms from them. The next day, I came to the Prophet (ﷺ) and found him with Abu Bakr, and they were both weeping I said: O Messenger of Allah , tell me why you and your companion are weeping. If I find it is a cause for weeping, I will weep too, and is it is not, then I will make myself weep with you. The Messenger of Allah (ﷺ) said: `I am weeping because of what your companions suggested about accepting a ransom for the prisoners. I have been shown your punishment as close as this tree` ­ a tree that was close to the Prophet (ﷺ) of Allah (ﷺ) Then Allah revealed the words:`It is not for a Prophet that he should have prisoners of war (and free them with ransom) until he had made a great slaughter (among his enemies) in the land. You desire the good of this world (i.e. the money of ransom for freeing the captives), but Allah desires (for you) the Hereafter. And Allah is Almighty, All Wise. Were it not a previous ordainment from Allah, a severe torment would have touched you for what you took `[al Anfal 8:67­-68] ­ i.e., referring to the ransom. Then booty was permitted to them, and when the day of Uhud came the following year, they were punished for what they had done of taking the ransom on the day of Badr. Seventy of them were killed and the Companions of the Prophet (ﷺ) deserted him, his front tooth was broken and the helmet on his head was broken, and blood flowed down his face, and Allah revealed the words: “When a single disaster smites you, although you smote (your enemies) with one twice as great, you say: 'From where does this come to us?`Say (to them), ‘It is from yourselves (because of your evil deeds).' And Allah has power over all things” [Al 'Imran 3:165]