Musannaf Ibn Abi Shayba 36:346

Muhammad ibn Bishr narrated to us, he said: Sa'id ibn Abi 'Aruba narrated to us, from Qatada, from Abu Nadra, from Abu Sa'id, he said: We went out with the Messenger of Allah, may Allah bless him and grant him peace, from Mecca to Khaybar when twelve days remained of Ramadan. A group of the companions of the Messenger of Allah, may Allah bless him and grant him peace, fasted, and others broke their fast, and neither found fault with the other.