Sunan an-Nasa'i 5089
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)."
أَخْبَرَنَا عَمْرُو بْنُ مَنْصُورٍ، قَالَ حَدَّثَنَا الْمُعَلَّى بْنُ أَسَدٍ، قَالَ حَدَّثَنَا مُطِيعُ بْنُ مَيْمُونٍ، حَدَّثَتْنَا صَفِيَّةُ بِنْتُ عِصْمَةَ، عَنْ عَائِشَةَ، أَنَّ امْرَأَةً، مَدَّتْ يَدَهَا إِلَى النَّبِيِّ صلى الله عليه وسلم بِكِتَابٍ فَقَبَضَ يَدَهُ فَقَالَتْ يَا رَسُولَ اللَّهِ مَدَدْتُ يَدِي إِلَيْكَ بِكِتَابٍ فَلَمْ تَأْخُذْهُ ‏.‏ فَقَالَ ‏"‏ إِنِّي لَمْ أَدْرِ أَيَدُ امْرَأَةٍ هِيَ أَوْ رَجُلٍ ‏"‏ ‏.‏ قَالَتْ بَلْ يَدُ امْرَأَةٍ ‏.‏ قَالَ ‏"‏ لَوْ كُنْتِ امْرَأَةً لَغَيَّرْتِ أَظْفَارَكِ بِالْحِنَّاءِ ‏"‏ ‏.‏