Sunan an-Nasa'i 2408
سنن النسائي#2408Sahihأَخْبَرَنَا زَكَرِيَّا بْنُ يَحْيَى، قَالَ حَدَّثَنَا عَبْدُ الأَعْلَى، قَالَ حَدَّثَنَا حَمَّادُ بْنُ سَلَمَةَ، عَنْ ثَابِتٍ، عَنْ أَبِي عُثْمَانَ، أَنَّ أَبَا هُرَيْرَةَ، قَالَ سَمِعْتُ رَسُولَ اللَّهِ صلى الله عليه وسلم يَقُولُ " شَهْرُ الصَّبْرِ وَثَلاَثَةُ أَيَّامٍ مِنْ كُلِّ شَهْرٍ صَوْمُ الدَّهْرِ " .
It was narrated that Abu Hurairah said:" I heard the Messenger of Allah say: 'The month of patience ( Ramadan) and three days of each month is fasting for a lifetime."' (Sahih)
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: 22:319