Musannaf Ibn Abi Shayba 27:709

Yazid ibn Harun narrated to us, from Hammad ibn Salamah, from Asim ibn Abi al-Najud, from Abu Salih, from Abu Hurayrah, who said: The Messenger of Allah (may Allah bless him and grant him peace) said: "Indeed, Allah, Blessed and Exalted is He, looked upon the people of Badr and said: 'Do what you wish, for I have already forgiven you.'"