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.
قَالَ رَسُولُ اللَّهِ ﷺ أَفْضَلُ الصَّلاَةِ بَعْدَ الْفَرِيضَةِ قِيَامُ اللَّيْلِ وَأَفْضَلُ الصِّيَامِ بَعْدَ رَمَضَانَ الْمُحَرَّمُ أَرْسَلَهُ شُعْبَةُ بْنُ الْحَجَّاجِ