Sauda, by Allah, you cannot conceal from us. Therefore, be careful when you go out. She ('A'isha) said: She turned back. Messenger of Allah ﷺ was at that time in my house having his evening meal and there was a bone in his hand. She (Sauda) cline and said: Messenger of Allah. I went out and 'Umar said to me so and so. She ('A'isha) reported: There came the revelation to him and then it was over; the bone was then in his hand and he had not thrown it and he said:" Permission has been granted to you that you may go out for your needs."  

يَا سَوْدَةُ وَاللَّهِ مَا تَخْفَيْنَ عَلَيْنَا فَانْظُرِي كَيْفَ تَخْرُجِينَ قَالَتْ فَانْكَفَأَتْ رَاجِعَةً وَرَسُولُ اللَّهِ ﷺ فِي بَيْتِي وَإِنَّهُ لَيَتَعَشَّى وَفِي يَدِهِ عَرْقٌ فَدَخَلَتْ فَقَالَتْ يَا رَسُولَ اللَّهِ إِنِّي خَرَجْتُ فَقَالَ لِي عُمَرُ كَذَا وَكَذَا قَالَتْ فَأُوحِيَ إِلَيْهِ ثُمَّ رُفِعَ عَنْهُ وَإِنَّ الْعَرْقَ فِي يَدِهِ مَا وَضَعَهُ فَقَالَ إِنَّهُ قَدْ أُذِنَ لَكُنَّ أَنْ تَخْرُجْنَ لِحَاجَتِكُنَّ وَفِي رِوَايَةِ أَبِي بَكْرٍ يَفْرَعُ النِّسَاءَ جِسْمُهَا زَادَ أَبُو بَكْرٍ فِي حَدِيثِهِ فَقَالَ هِشَامٌ يَعْنِي الْبَرَازَ  

She (Sauda) was a woman who looked to be significant amongst the people (so far as the bulk of her) body was concerned. The rest of the hadith is the same.  

وَقَالَ وَكَانَتِ امْرَأَةً يَفْرَعُ النَّاسَ جِسْمُهَا قَالَ وَإِنَّهُ لَيَتَعَشَّى وَحَدَّثَنِيهِ سُوَيْدُ بْنُ سَعِيدٍ حَدَّثَنَا عَلِيُّ بْنُ مُسْهِرٍ عَنْ هِشَامٍ بِهَذَا الإِسْنَادِ  

Messenger of Allah, ask your ladies to observe veil, but Messenger of Allah ﷺ did not do that. So there went out Sauda, daughter of Zarn'a, the wife of Messenger of Allah ﷺ, during one of the nights when it was dark. She was a tall statured lady. 'Umar called her saying: Sauda, we recognise you. (He did this with the hope that the verses pertaining to veil would be revealed.) 'A'isha said: Allah, the Exalted and Glorious, then revealed the verses pertaining to veil.  

أَنَّ أَزْوَاجَ رَسُولِ اللَّهِ ﷺ كُنَّ يَخْرُجْنَ بِاللَّيْلِ إِذَا تَبَرَّزْنَ إِلَى الْمَنَاصِعِ وَهُوَ صَعِيدٌ أَفْيَحُ وَكَانَ عُمَرُ بْنُ الْخَطَّابِ يَقُولُ لِرَسُولِ اللَّهِ ﷺ احْجُبْ نِسَاءَكَ فَلَمْ يَكُنْ رَسُولُ اللَّهِ ﷺ يَفْعَلُ فَخَرَجَتْ سَوْدَةُ بِنْتُ زَمْعَةَ زَوْجُ النَّبِيِّ ﷺ لَيْلَةً مِنَ اللَّيَالِي عِشَاءً وَكَانَتِ امْرَأَةً طَوِيلَةً فَنَادَاهَا عُمَرُ أَلاَ قَدْ عَرَفْنَاكِ يَا سَوْدَةُ حِرْصًا عَلَى أَنْ يُنْزِلَ الْحِجَابَ قَالَتْ عَائِشَةُ فَأَنْزَلَ اللَّهُ ﷻ الْحِجَابَ  

This hadith has been narrated on the authority of Ibn Shihab with the same chain of transmitters.  

عَنِ ابْنِ شِهَابٍ بِهَذَا الإِسْنَادِ نَحْوَهُ