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" (ES)
English reference (ES): Book 10, Hadith 71 (ES)
Arabic reference (ES): Book 11, Hadith 75 (ES)