Sunan An-Nasa'i

It was narrated from 'Aishah that:A woman reached out her hand (to give) a letter to the Prophet [SAW], and he withdrew his hand. She said: ""O Messenger of Allah, I reached out my hand (to give you) a letter and you did not take it."" He said: ""I did not know whether it was the hand of a woman or a man."" She said: ""It is the hand of a woman."" He said: ""If you were a woman, you would change your nails (by dyeing them with Henna)