Sunan Abi Dawud 962
سنن أبي داود#962Da'ifحَدَّثَنَا هَنَّادُ بْنُ السَّرِيِّ، عَنْ وَكِيعٍ، عَنْ سُفْيَانَ، عَنِ الزُّبَيْرِ بْنِ عَدِيٍّ، عَنْ إِبْرَاهِيمَ، قَالَ كَانَ النَّبِيُّ صلى الله عليه وسلم إِذَا جَلَسَ فِي الصَّلاَةِ افْتَرَشَ رِجْلَهُ الْيُسْرَى حَتَّى اسْوَدَّ ظَهْرُ قَدَمِهِ .
It was reported from Ibrahim that he said:"When the Prophet (ﷺ) would sit in the prayer, he would place his left foot horizontally - so much so that the upper-part of his foot became black
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-AlbaniDaif
Muhammad Muhyi Al-Din Abdul HamidDaif
Zubair Ali ZaiDaif
In-book reference: 2:573