Sahih Bukhari Volume 007, Book 065, Hadith Number 324.
Narrated By Abu Hazim : I asked Sahl bin Sad, "Did Allah's Apostle ever eat white flour?" Sahl said, "Allah's Apostle never saw white flour since Allah sent him as an Apostle till He took him unto Him." I asked, "Did the people have (use) sieves during the lifetime of Allah's Apostle?" Sahl said, "Allah's Apostle never saw (used) a sieve since Allah sent him as an Apostle until He took him unto Him," I said, "How could you eat barley unsifted?" he said, "We used to grind it and then blow off its husk, and after the husk flew away, we used to prepare the dough (bake) and eat it."