Musannaf Ibn Abi Shayba 36:122

Al-Fadl ibn Dukayn narrated to us, he said: 'Amr ibn Shabba narrated to us, he said: I asked Abu Bakr ibn 'Abd al-Rahman ibn al-Harith ibn Hisham: "Which night was the night of Badr?" He said: "It was the night of Friday, when seventeen nights had passed of Ramadan."