Hadithcore
Sahih Muslim, 1310 b
sahih

Nafi' reported that Ibn 'Umar regarded halt at Muhassab as Sunnah (of the Prophet) and observed the noon prayer on Yaum al-Nafr at that place. Nafi' said:

Allah's Messenger (ﷺ) halted at Muhassab and the Caliphs did the same after him.

حَدَّثَنِي مُحَمَّدُ بْنُ حَاتِمِ بْنِ مَيْمُونٍ، حَدَّثَنَا رَوْحُ بْنُ عُبَادَةَ، حَدَّثَنَا صَخْرُ بْنُ جُوَيْرِيَةَ، عَنْ نَافِعٍ، أَنَّ ابْنَ عُمَرَ، كَانَ يَرَى التَّحْصِيبَ سُنَّةً وَكَانَ يُصَلِّي الظُّهْرَ يَوْمَ النَّفْرِ بِالْحَصْبَةِ ‏.‏ قَالَ نَافِعٌ قَدْ حَصَّبَ رَسُولُ اللَّهِ صلى الله عليه وسلم وَالْخُلَفَاءُ بَعْدَهُ ‏.‏

References2 variants
In-Book Reference
Book 15, Hadith 372
USC-MSA web (English) reference
Book 7, Hadith 3007 (deprecated numbering scheme)