Sunan an-Nasa'i 2418
سنن النسائي#2418Sahihأَخْبَرَنَا مُحَمَّدُ بْنُ عُثْمَانَ بْنِ أَبِي صَفْوَانَ الثَّقَفِيُّ، قَالَ حَدَّثَنَا عَبْدُ الرَّحْمَنِ، قَالَ حَدَّثَنَا أَبُو عَوَانَةَ، عَنِ الْحُرِّ بْنِ الصَّيَّاحِ، عَنْ هُنَيْدَةَ بْنِ خَالِدٍ، عَنِ امْرَأَتِهِ، عَنْ بَعْضِ، أَزْوَاجِ النَّبِيِّ صلى الله عليه وسلم قَالَتْ كَانَ النَّبِيُّ صلى الله عليه وسلم يَصُومُ الْعَشْرَ وَثَلاَثَةَ أَيَّامٍ مِنْ كُلِّ شَهْرٍ الاِثْنَيْنِ وَالْخَمِيسَ .
It was narrated from Hunaidah bin Khalid, from his wife, that one of the wives of the Prophet said:"The Prophet used to fast the ten (days), and three days of each month: Monday and Thursday
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:
In-book reference: 22:329