Some of the wives of the Prophet ﷺ asked him, "Who amongst us will be the first to follow you (i.e. die after you)?" He said, "Whoever has the longest hand." So they started measuring their hands with a stick and Sauda's hand turned out to be the longest. (When Zainab bint Jahsh died first of all in the caliphate of ʿUmar), we came to know that the long hand was a symbol of practicing charity, so she was the first to follow the Prophet ﷺ and she used to love to practice charity.  

أَنَّ بَعْضَ أَزْوَاجِ النَّبِيِّ ﷺ قُلْنَ لِلنَّبِيِّ ﷺ أَيُّنَا أَسْرَعُ بِكَ لُحُوقًا? قَالَ: «أَطْوَلُكُنَّ يَدًا۔» فَأَخَذُوا قَصَبَةً يَذْرَعُونَهَا فَكَانَتْ سَوْدَةُ أَطْوَلَهُنَّ يَدًا۔ فَعَلِمْنَا بَعْدُ أَنَّمَا كَانَتْ طُولَ يَدِهَا الصَّدَقَةُ وَكَانَتْ أَسْرَعَنَا لُحُوقًا بِهِ وَكَانَتْ تُحِبُّ الصَّدَقَةَ  

"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.  

أَنَّ أَزْوَاجَ النَّبِيِّ ﷺ 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