سنن النسائي

It was narrated from 'Aishah that: A woman reached out her hand (to give) a letter to the Prophet (ﷺ) [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)."