Narrated Aisha, Ummul Mu'minin:A woman made a sign from behind a curtain to indicate that she had a letter for the Messenger of Allah (ﷺ). The Prophet (ﷺ) closed his hand, saying: I do not know this is a man's or a woman's hand. She said: No, a woman. He said: If you were a woman, you would make a difference to your nails, meaning with henna.
حَدَّثَنَا مُحَمَّدُ بْنُ مُحَمَّدٍ الصُّورِيُّ، حَدَّثَنَا خَالِدُ بْنُ عَبْدِ الرَّحْمَنِ، حَدَّثَنَا مُطِيعُ بْنُ مَيْمُونٍ، عَنْ صَفِيَّةَ بِنْتِ عِصْمَةَ، عَنْ عَائِشَةَ، - رضى الله عنها - قَالَتْ أَوْمَتِ امْرَأَةٌ مِنْ وَرَاءِ سِتْرٍ بِيَدِهَا كِتَابٌ إِلَى رَسُولِ اللَّهِ صلى الله عليه وسلم فَقَبَضَ النَّبِيُّ صلى الله عليه وسلم يَدَهُ فَقَالَ " مَا أَدْرِي أَيَدُ رَجُلٍ أَمْ يَدُ امْرَأَةٍ " . قَالَتْ بَلِ امْرَأَةٌ . قَالَ " لَوْ كُنْتِ امْرَأَةً لَغَيَّرْتِ أَظْفَارَكِ " . يَعْنِي بِالْحِنَّاءِ .
AbuDaud
Combing the Hair (Kitab Al-Tarajjul) • Hadith 4166