Musnad Ahmad 25:394

Nasr ibn Bab narrated to us, from al-Hajjaj, from al-Hakam, from Miqsam, from Ibn Abbas, that he said: "The people of Badr were three hundred and thirteen men. The Emigrants (Muhajirun) were seventy-six. The defeat of the people of Badr was on the seventeenth [day] that had passed of the month of Ramadan, on a Friday."