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.
أَخْبَرَنَا 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 .
Nesai
The Book of Qiyam Al-Lail (The Night Prayer) and Voluntary Prayers During the Day • Hadith 1614