Sunan Abi Dawud 962

Arabic

حَدَّثَنَا 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 ‏.‏

Translation

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

Authenticity

Da'if · Al-Albani

Reference