Sunan an-Nasai Book 23, Hadith 2541

أَخْبَرَنَا أَبُو دَاوُدَ، قَالَ حَدَّثَنَا يَحْيَى بْنُ حَمَّادٍ، قَالَ أَنْبَأَنَا أَبُو عَوَانَةَ، عَنْ فِرَاسٍ، عَنْ عَامِرٍ، عَنْ مَسْرُوقٍ، عَنْ عَائِشَةَ، رضى الله عنها أَنَّ أَزْوَاجَ، النَّبِيِّ صلى الله عليه وسلم اجْتَمَعْنَ عِنْدَهُ فَقُلْنَ أَيَّتُنَا بِكَ أَسْرَعُ لُحُوقًا فَقَالَ ‏ "‏ أَطْوَلُكُنَّ يَدًا ‏"‏ ‏.‏ فَأَخَذْنَ قَصَبَةً فَجَعَلْنَ يَذْرَعْنَهَا فَكَانَتْ سَوْدَةُ أَسْرَعَهُنَّ بِهِ لُحُوقًا فَكَانَتْ أَطْوَلَهُنَّ يَدًا فَكَانَ ذَلِكَ مِنْ كَثْرَةِ الصَّدَقَةِ ‏.‏

It was narrated from 'Aishah, may Allah be pleased with her, that the wives of the Prophet "gathered around him and said:"Which of us will be the first to following you (in death)?" He said: "The one of you who has the longest arms." They took a stick and started to measure their arms. But Sawdah was the first one to follow him. She was the one who had the longest arms, because she used to give in charity a great deal