Ibn ‘Umar reported God’s Messenger as saying, "Avoid being naked, for with you are those who never leave you (the recording angels) except when you are relieving yourselves and when a man has intercourse with his wife; so observe modesty before them and honour them.”
Muhammad b. Jahsh told that God’s Messenger came upon Ma'mar when his thighs were uncovered and said, "Cover your thighs, Ma'mar, for the thighs are private parts.”
I was with God’s Messenger along with Maimuna when Ibn Umm Maktum approached and came in to visit him, so he told us to veil ourselves. I said, "Messenger of God, is he not blind and unable to see us?” He replied, "Are you blind and unable to see him?”