Musannaf Ibn Abi Shayba 36:185

'A'idh ibn Habib narrated to us, from Hajjaj, from al-Hakam, from al-Miqsam, from Ibn 'Abbas: That the people of Badr were three hundred and thirteen. The Emigrants (Muhajirun) among them were seventy-five. The defeat of Badr was on the seventeenth of Ramadan, on the night of Friday.