Musannaf Ibn Abi Shayba 36:74

Abu Bakr narrated to us, he said: Abu Usamah narrated to us, he said: Hisham ibn Urwah narrated to us, from his father, and Fatimah, from Asma, who said: I prepared the provisions (sufrah) for the Prophet, may Allah bless him and grant him peace, in the house of Abu Bakr when he intended to migrate to Medina. She said: We did not find anything for his provisions nor for his water skin to tie them with. So I said to Abu Bakr: By Allah, I do not find anything to tie them with except my waistband (nitaq). She said: He said: Tear it into two, and tie the water skin with one, and the provisions with the other. For that reason, she was named Dhat al-Nitaqayn (The Possessor of the Two Waistbands).