Sahih Muslim | Book 26 | Hadith Number 5395
Narrated by 'Aisha
'Aisha reported that Sauda (Allah he pleated with her) went out (in the fields) in order to answer the call of nature even after the time when veil had been prescribed for women. She had been a bulky lady, significant in height amongst the women, and she could not conceal herself from him who had known her. 'Umar b. Khattab saw her and said: Sauda, by Allah, you cannot conceal from us. Therefore, be careful when you go out. She ('Aisha) said: She turned back. Allah's Messenger (may peace be upon him) was at that time in my house having his evening meal and there was a bone in his hand. She (Sauda) cline and said: Allah's Messenger. I went out and 'Umar said to me so and so. She ('Aisha) 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.