Sahih Muslim 2402 a
A'isha, the wife of Allah's Apostle (mav peace be upon him), and Uthman both reported that Abu Bakr sought permission from Allah's Messenger (ﷺ) for entrance (in his apartment) as he had been lying on his bed covered with the bed-sheet of A'isha, and he gave permission to Abu Bakr in that very state and he, having his need fulfilled, went back. Then Umar sought permission and it was given to him in that very state and, after having his need fulfilled, he went back. And 'Uthman reported:
Then I sought permission from him and he got up and raid to A'isha: Wrap yourself well with your cloth, then I got my need fulfilled and came back. And A'isha said: Allah's Messenger, why is it that I did not see you feeling any anxiety in case of dressing properly in the presence of Abu Bakr and 'Umar (Allah be pleased with them) as you showed in case of 'Uthman. Thereupon Allah's Messenger (ﷺ) said: Verily Uthman is a person who is very modest and I was afraid that if I permitted him to enter in this very state he would not inform me of his need.
حَدَّثَنَا عَبْدُ الْمَلِكِ بْنُ شُعَيْبِ بْنِ اللَّيْثِ بْنِ سَعْدٍ، حَدَّثَنِي أَبِي، عَنْ جَدِّي، حَدَّثَنِي عُقَيْلُ،
 بْنُ خَالِدٍ عَنِ ابْنِ شِهَابٍ، عَنْ يَحْيَى بْنِ سَعِيدِ بْنِ الْعَاصِ، أَنَّ سَعِيدَ بْنَ الْعَاصِ، أَخْبَرَهُ أَنَّ
 عَائِشَةَ زَوْجَ النَّبِيِّ صلى الله عليه وسلم وَعُثْمَانَ حَدَّثَاهُ أَنَّ أَبَا بَكْرٍ اسْتَأْذَنَ عَلَى رَسُولِ
 اللَّهِ صلى الله عليه وسلم وَهُوَ مُضْطَجِعٌ عَلَى فِرَاشِهِ لاَبِسٌ مِرْطَ عَائِشَةَ فَأَذِنَ لأَبِي بَكْرٍ
 وَهُوَ كَذَلِكَ فَقَضَى إِلَيْهِ حَاجَتَهُ ثُمَّ انْصَرَفَ ثُمَّ اسْتَأْذَنَ عُمَرُ فَأَذِنَ لَهُ وَهُوَ عَلَى تِلْكَ الْحَالِ
 فَقَضَى إِلَيْهِ حَاجَتَهُ ثُمَّ انْصَرَفَ ‏.‏ قَالَ عُثْمَانُ ثُمَّ اسْتَأْذَنْتُ عَلَيْهِ فَجَلَسَ وَقَالَ لِعَائِشَةَ ‏"‏
 اجْمَعِي عَلَيْكِ ثِيَابَكِ ‏"‏ ‏.‏ فَقَضَيْتُ إِلَيْهِ حَاجَتِي ثُمَّ انْصَرَفْتُ فَقَالَتْ عَائِشَةُ يَا رَسُولَ اللَّهِ
 مَا لِي لَمْ أَرَكَ فَزِعْتَ لأَبِي بَكْرٍ وَعُمَرَ رَضِيَ اللَّهُ عَنْهُمَا كَمَا فَزِعْتَ لِعُثْمَانَ قَالَ رَسُولُ
 اللَّهِ صلى الله عليه وسلم ‏"‏ إِنَّ عُثْمَانَ رَجُلٌ حَيِيٌّ وَإِنِّي خَشِيتُ إِنْ أَذِنْتُ لَهُ عَلَى تِلْكَ الْحَالِ
 أَنْ لاَ يَبْلُغَ إِلَىَّ فِي حَاجَتِهِ ‏"‏ ‏.‏