The Messenger of Allah ﷺ said, "The one among you with the longest arm will be the quickest to follow me."She said, "So they began comparing their arms to see whose was the longest. The one with the longest arm turned out to be Zaynab, because she used to work with her hands and give in charity."
قال رسول الله ﷺ: أسرعكن لحاقا بي أطولكن يدا. قالت: فكن يتطاولن أيتهن أطول يدا. قالت: فكانت أطولنا يدا زينب؛ لأنها كانت تعمل بيدها، وتصدق.
Muslim narrated it in Fadail al-Sahabah (2452) from Mahmud bin Ghaylan, who said, Fadl bin Musa Sinani told us, Talha bin Yahya bin Talha informed us, from Ayesha bint Talha, from Ayesha, mother of the believers, and she related it.What the Prophet ﷺ meant by "longest hand" was abundance of charity, not literal length of the hand. Zaynab was, by the agreement of the biographers, the first of his wives to join him in death, and she was indeed abundant in charity. From this one recognizes the error that occurred in the following hadith of Bukhari.