Sunan an-Nasa'i 1614
سنن النسائي#1614SahihIt 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
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Abu GhuddahSahih Lighairihi
Al-AlbaniSahih
Zubair Ali ZaiHasan
In-book reference: 20:17