Sunan an-Nasa'i 1614
سنن النسائي#1614Sahihأَخْبَرَنَا سُوَيْدُ بْنُ نَصْرٍ، قَالَ أَنْبَأَنَا عَبْدُ اللَّهِ، قَالَ حَدَّثَنَا شُعْبَةُ، عَنْ أَبِي بِشْرٍ، جَعْفَرِ بْنِ أَبِي وَحْشِيَّةَ أَنَّهُ سَمِعَ حُمَيْدَ بْنَ عَبْدِ الرَّحْمَنِ، يَقُولُ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " أَفْضَلُ الصَّلاَةِ بَعْدَ الْفَرِيضَةِ قِيَامُ اللَّيْلِ وَأَفْضَلُ الصِّيَامِ بَعْدَ رَمَضَانَ الْمُحَرَّمُ " . أَرْسَلَهُ شُعْبَةُ بْنُ الْحَجَّاجِ .
It was narrated from Abu Bishr Ja'far bin Abi Wahshiyyah that:He heard Humaid bin 'Abdur-Rahman say: "The Messenger of Allah (ﷺ) said: 'The best prayer after the obligatory (fard) prayers is prayer at night and the best fasting after the month of Ramadan is Al-Muharram.'" Shu'bah bin Al-Hajjaj narrated it in Mursal form
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: 20:17