From Sahih Bukhari (Hadith 2979):
Narrated Asma:I prepared the journey-food for Allah's Messenger (ﷺ) 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 subnarrator added, "She did accordingly and that was the reason for calling her Dhatun-Nitaqain (i.e. two-belted woman)
Reference: Bukhari 2979