Musnad Ahmad 30:822

Yazid narrated to us, Hammad ibn Salamah informed us, from ‘Asim ibn Abi al-Najud, from Abu Salih, from Abu Hurairah, from the Messenger of Allah (may Allah bless him and grant him peace), who said: "Indeed, Allah the Almighty and Majestic looked upon the people of Badr and said: 'Do whatever you wish, for I have already forgiven you.'"