Hadith 4467
She told that a woman made a sign from behind a curtain to indicate that she had a letter for God's messenger. The Prophet closed his hand saying, “I do not know whether this is a man’s or a woman’s hand," and when she declared that it was a woman’s he said, “If you were a woman you would make a difference to your nails," meaning with henna. Abu Dawud and Nasa'i transmitted it.
وَعَنْهَا قَالَتْ: أَوَمَتِ امْرَأَةٌ مِنْ وَرَاءِ سِتْرٍ بِيَدِهَا كِتَابٌ إِلَى رَسُولِ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ فَقَبَضَ النَّبِيُّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ يَدَهُ فَقَالَ: «مَا أَدْرِي أَيَدُ رَجُلٍ أَمْ يَدُ امْرَأَةٍ؟» قَالَتْ: بَلْ يَدُ امْرَأَةٍ قَالَ: «لَوْ كُنْتِ امْرَأَةً لَغَيَّرْتِ أَظْفَارَكِ» يَعْنِي الْحِنَّاء. رَوَاهُ أَبُو دَاوُد وَالنَّسَائِيّ