Sahih Bukhari Volume 4, Book 52, Hadith Number 222.

Narated By Asma : I prepared the journey-food for Allah’s Apostle in Abu Bakr’s house when he intended to emigrate to Medina. I could not find anything to tie the food-container and the water skin with. So, I said to Abu Bakr, “By Allah, I do not find anything to tie (these things) with except my waist belt.” He said, “Cut it into two pieces and tie the water-skin with one piece and the food-container with the other (the sub-narrator added, “She did accordingly and that was the reason for calling her Dhatun-Nitaqain (i.e. two-belted woman)).”