The sandals of the Messenger of Allah ﷺ had two straps.
كان لنعل رسول الله ﷺ قبالان.
No references are available.
Tirmidhi narrated it in Shamail (75), and Tabarani in Saghir (254), both of them by way of Abdul-Razzaq, who said, Muammar narrated to us, from Ibn Abu Dhib, from Salih the freedman of Tawama, from Abu Hurairah, who said, then he related it.Its isnad is hasan because of Salih the freedman of Tawama, who is Salih bin Nabhan. Hafiz said of him, "He was truthful, but became confused in his later years." Ibn Abu Dhib's hearing from him was before that confusion set in, as the leading scholars have stated, except that Bukhari said, "I do not think he heard from him in his early years, he narrates objectionable reports from him." And Allah Most High knows best.Tabarani added in the hadith, "Abu Bakr's sandal had two straps, Umar's sandal had two straps, and the first to fasten a single strap was Uthman ." This addition is daif because of the obscurity of Tabarani's teacher, who is Ibrahim bin Ishaq al-Dawardi al-Tabarani, whose condition is not known.This addition was also narrated by Tirmidhi in Shamail (81) through another route from Abu Hurairah, except that its isnad contains Abdul-Rahman bin Qays Abu Muawiya, who is discarded as a narrator, Abu Zura and others accused him of lying.