Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) said: Once the Messenger of Allah (peace and blessings be upon him) was sitting, and Sayyidah Aishah (may Allah be pleased with her) was behind him (peace and blessings be upon him), when Sayyiduna Abu Bakr (may Allah be pleased with him) asked permission and came in; then Sayyiduna Umar (may Allah be pleased with him) asked permission and came in; then Sa'd bin Malik (may Allah be pleased with him) asked permission and came in; then Sayyiduna Uthman bin Affan (may Allah be pleased with him) asked permission. The Messenger of Allah (peace and blessings be upon him) was talking at that time with his (peace and blessings be upon him) knee uncovered; so when Uthman (may Allah be pleased with him) asked permission, he (peace and blessings be upon him) drew his garment over his knee and said to his wife: Move back. Then they all talked for a while, and then they left. Sayyidah Aishah (may Allah be pleased with her) said: O Prophet of Allah! My father and his companions came in, and you (peace and blessings be upon him) did not adjust your garment over your knee, nor did you move me away from you? At this the Prophet (peace and blessings be upon him) said: "O Aishah, should I not feel shy before a man before whom the angels feel shy? By the One in whose Hand is the soul of the Messenger of Allah (peace and blessings be upon him), the angels feel shy before Uthman just as they feel shy before Allah and His Messenger. And had he come in while you were near me, he would neither have spoken nor raised his head until you had left."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 13196