Sunan an-Nasa'i 2359
سنن النسائي#2359Sahihأَخْبَرَنَا أَحْمَدُ بْنُ سُلَيْمَانَ، قَالَ حَدَّثَنَا زَيْدُ بْنُ الْحُبَابِ، قَالَ أَخْبَرَنِي ثَابِتُ بْنُ قَيْسٍ الْغِفَارِيُّ، قَالَ حَدَّثَنِي أَبُو سَعِيدٍ الْمَقْبُرِيُّ، قَالَ حَدَّثَنِي أَبُو هُرَيْرَةَ، عَنْ أُسَامَةَ بْنِ زَيْدٍ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم كَانَ يَسْرُدُ الصَّوْمَ فَيُقَالُ لاَ يُفْطِرُ وَيُفْطِرُ فَيُقَالُ لاَ يَصُومُ .
It was narrated from Usamah bin Zaid:That the Messenger of Allah used to fast continually and it ws said that he would not break his fast, and he used not to fast and it was said that he would not fast
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: 22:270