Sahih Muslim
The Book Pertaining to the Merits of the Companions (Allah Be Pleased With Them) of the Holy Prophet (May Peace Be Upon Him) (Kitab Al-Fadail Al-Sahabah)
Book Number: 031 / Hadith Number: 6007
'A'isha, the Mother of the Faithful, reported that Allah's Messenger (may peace be upon him) said: One who has the longest hands amongst you would meet me most immediately. She farther said: They (the wives of Allah's Apostle) used to measure the hands as to whose hand was the longest and it was the hand of Zainab that was the longest amongst them, as she used to work with her hand and Spend (that income) on charity.