Hadithcore
Mishkat al-Masabih, 4408

Anas said the Prophet’s sandal had two thongs. Bukhari transmitted it.

وَعَنْ أَنَسٍ قَالَ: إِنَّ نَعْلَ النَّبِيِّ صَلَّى الله عَلَيْهِ وَسلم كَانَ لَهَا قبالان

References1 variant
In-Book Reference
Book 22, Hadith 98