Sunan Abi Dawud 148
سنن أبي داود#148Sahihحَدَّثَنَا قُتَيْبَةُ بْنُ سَعِيدٍ، حَدَّثَنَا ابْنُ لَهِيعَةَ، عَنْ يَزِيدَ بْنِ عَمْرٍو، عَنْ أَبِي عَبْدِ الرَّحْمَنِ الْحُبُلِيِّ، عَنِ الْمُسْتَوْرِدِ بْنِ شَدَّادٍ، قَالَ رَأَيْتُ رَسُولَ اللَّهِ صلى الله عليه وسلم إِذَا تَوَضَّأَ يَدْلُكُ أَصَابِعَ رِجْلَيْهِ بِخِنْصَرِهِ .
Narrated Al-Mustawrid ibn Shaddad: I saw the Messenger of Allah (ﷺ) rubbing his toes with his little finger when he performed ablution
Scholarly Authentication
The label above is the grade most of these scholars gave — one dissenting opinion no longer speaks for all of them. If any scholar calls a narration fabricated, that verdict is shown instead, whatever the others say. Each scholar's own wording:
Al-AlbaniSahih
Muhammad Muhyi Al-Din Abdul HamidSahih
Shuaib Al ArnautSahih Lighairihi
Zubair Ali ZaiHasan
In-book reference: 1:148