Musnad Ahmad 1167:17

Abu Usamah narrated to us, he said: Hisham narrated to us, from his father, and Fatimah, from Asma, who said: "I prepared the provisions (sufrah) for the Messenger of Allah, peace and blessings of Allah be upon him, in the house of Abu Bakr when he intended to migrate." She said: "We did not find anything for his provisions nor for his water skin to tie them with." She said: "So I said to Abu Bakr: 'By Allah, I do not find anything to tie them with except my waistband (nitaq).' He said: 'Split it into two; tie the water skin with one, and the provisions with the other.' And for that reason, she was named Dhat an-Nitaqayn (The One with the Two Waistbands)."