Qataadah radiallahu anhu reports that:
"I asked Anas to describe the shoe of Rasulullah Sayyidina Rasulullah sallallahu alaihe wasallam". He replied: "Each shoe had two straps" (ID)
English reference (ID): Book 10, Hadith 71 (ID)
Arabic reference (ID): Book 11, Hadith 75 (ID)