Sahih al-Bukhari 4795
Narrated Aisha:
Sauda (the wife of the Prophet) went out to answer the call of nature after it was made obligatory (for 
all the Muslims ladies) to observe the veil. She had a large frame and everybody who knew her 
before could recognize her. So `Umar bin Al-Khattab saw her and said, "O Sauda! By Allah, you 
cannot hide yourself from us, so think of a way by which you should not be recognized on going out. 
Sauda returned while Allah's Messenger (ﷺ) was in my house taking his supper and a bone covered with 
meat was in his hand. She entered and said, "O Allah's Messenger (ﷺ)! I went out to answer the call of nature 
and `Umar said to me so-and-so." Then Allah inspired him (the Prophet) and when the state of 
inspiration was over and the bone was still in his hand as he had not put in down, he said (to Sauda), 
"You (women) have been allowed to go out for your needs."
حَدَّثَنِي زَكَرِيَّاءُ بْنُ يَحْيَى، حَدَّثَنَا أَبُو أُسَامَةَ، عَنْ هِشَامٍ، عَنْ أَبِيهِ، عَنْ عَائِشَةَ ـ رضى الله عنها ـ قَالَتْ خَرَجَتْ سَوْدَةُ بَعْدَ مَا ضُرِبَ الْحِجَابُ لِحَاجَتِهَا، وَكَانَتِ امْرَأَةً جَسِيمَةً لاَ تَخْفَى عَلَى مَنْ يَعْرِفُهَا، فَرَآهَا عُمَرُ بْنُ الْخَطَّابِ فَقَالَ يَا سَوْدَةُ أَمَا وَاللَّهِ مَا تَخْفَيْنَ عَلَيْنَا، فَانْظُرِي كَيْفَ تَخْرُجِينَ، قَالَتْ فَانْكَفَأَتْ رَاجِعَةً، وَرَسُولُ اللَّهِ صلى الله عليه وسلم فِي بَيْتِي، وَإِنَّهُ لَيَتَعَشَّى‏.‏ وَفِي يَدِهِ عَرْقٌ فَدَخَلَتْ فَقَالَتْ يَا رَسُولَ اللَّهِ إِنِّي خَرَجْتُ لِبَعْضِ حَاجَتِي فَقَالَ لِي عُمَرُ كَذَا وَكَذَا‏.‏ قَالَتْ فَأَوْحَى اللَّهُ إِلَيْهِ ثُمَّ رُفِعَ عَنْهُ وَإِنَّ الْعَرْقَ فِي يَدِهِ مَا وَضَعَهُ فَقَالَ ‏
"‏ إِنَّهُ قَدْ أُذِنَ لَكُنَّ أَنْ تَخْرُجْنَ لِحَاجَتِكُنَّ ‏"‏‏.‏