It is narrated from Abdullah bin Abi Sa'id al-Madini that Hafsah bint Umar (may Allah be pleased with her) said: One day the Messenger of Allah (peace and blessings be upon him) was sitting with his garment placed between his thighs. Abu Bakr (may Allah be pleased with him) came and asked permission; the Messenger of Allah (peace and blessings be upon him) gave him permission and he (peace and blessings be upon him) remained sitting as he was. Then Umar (may Allah be pleased with him) came and the same happened. Then Ali (may Allah be pleased with him) came, then other people kept coming and going, and he (peace and blessings be upon him) remained sitting as he was. Then Sayyiduna Uthman (may Allah be pleased with him) came and asked permission, and the Messenger of Allah (peace and blessings be upon him) arranged his garment. Hafsah (may Allah be pleased with her) said: The people sat talking and then left. I said: O Messenger of Allah (peace and blessings be upon him)! Abu Bakr (may Allah be pleased with him) came, Umar (may Allah be pleased with him) came, Ali (may Allah be pleased with him) came, and the rest of your Companions (may Allah be pleased with them) came, yet you remained sitting in the same state; but when Uthman (may Allah be pleased with him) came, you immediately arranged your garment? The Messenger of Allah (peace and blessings be upon him) said: "Should I not feel shy before the man before whom even the angels feel shy?"
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3244