Musnad Abu Ya'la al-Mawsili 115:193

Muhammad narrated to us, Abd al-Razzaq narrated to us, Ma'mar informed us, from Qatadah, from Anas, who said: When the funeral of Sa'd ibn Mu'adh was carried, the hypocrites said, "How light his funeral is!" And that was because of his judgment regarding Banu Qurayzah. This reached the Prophet, peace and blessings of Allah be upon him, so he said, "Indeed, the angels were carrying him."