The sandal of the Prophet (ﷺ) had two straps.
Sahih al-Bukhari Book 77, Hadith 74
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Sahih al-Bukhari Book 77, Hadith 73 Next Hadith → Anas bin Malik brought out for us, two sandals having two straps. Thabit Al-Banani said, "These were the sandals of the Prophet (ﷺ) ."

Sahih al-Bukhari Book 77, Hadith 75