Musannaf Ibn Abi Shayba 36:126

'Abd al-Rahim ibn Sulayman narrated to us, from Muhammad ibn 'Amr al-Laythi, from his grandfather, who said: The Messenger of Allah (may Allah bless him and grant him peace) went out to Badr. When he was at al-Rawha', he addressed the people and said: "What do you think?" Abu Bakr said: "O Messenger of Allah, it has reached us that they are such and such." Then he addressed the people and said: "What do you think?" 'Umar said the like of what Abu Bakr said. Then he addressed [them] and said: "What do you think?" Sa'd ibn Mu'adh said: "Is it us you want? By the One who honored you and revealed the Book to you, I have never traveled it [this path], nor do I have knowledge of it. If you were to travel until you reached Bark al-Ghimad in Yemen, we would travel with you. We will not be like those who said to Musa from the Children of Israel: 'So go, you and your Lord, and fight; indeed, we are sitting right here.' Rather, go, you and your Lord, and fight; indeed, we are with you, following. Perhaps you went out for a matter, and Allah brought about something else for you; so look to what Allah has brought about for you and proceed with it. Connect the ties of whomever you wish, sever the ties of whomever you wish, make peace with whomever you wish, show enmity to whomever you wish, and take from our wealth whatever you wish." Then the Quran was revealed regarding the statement of Sa'd: "Just as your Lord brought you out of your house in truth, while a party of the believers..." until His saying: "...and cut off the roots of the disbelievers." The Messenger of Allah (may Allah bless him and grant him peace) had only gone out desiring the spoils that were with Abu Sufyan, but Allah brought about the fighting for him.