Musnad Ahmad 31:869

Hajjaj narrated to us, Shu'bah narrated to me, from Qatadah, who said: I heard Abu Nadrah, from Abu Sa'id al-Khudri, who said: "We went out with the Prophet, peace and blessings of Allah be upon him, on the eighteenth day that had passed of Ramadan. So, some fasted and some broke their fast, and those who fasted did not criticize those who broke their fast, nor did those who broke their fast criticize those who fasted." Shu'bah said: "Four people narrated this hadith to me, one of whom was Qatadah, and this is the hadith of Qatadah."