Hadithcore
Mishkat al-Masabih, 3528

Al-Hasan said on Samura’s authority that God’s Messenger forbade that a thong of a sandal should be cut off between two toes. Abu Dawud transmitted it.

وَعَن الحسنِ عَنْ سَمُرَةَ أَنَّ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ نَهَى أَنْ يُقَدَّ السَّيْرُ بَيْنَ أُصبعَينِ. رَوَاهُ أَبُو دَاوُد

References1 variant
In-Book Reference
Book 16, Hadith 75