Musnad Ahmad 31:861

Abu Dawud narrated to us, Shu'bah narrated to us, from Qatadah, who said: I heard Abdullah ibn Abi Utbah narrating from Abu Sa'id al-Khudri, who said: "The Messenger of Allah (peace and blessings of Allah be upon him) was more bashful than a virgin in her private quarters. And whenever he disliked something, we would recognize it in his face."