Hadithcore
Mishkat al-Masabih, 1262

Abu Huraira said, ‘‘My friend* instructed me to observe three practices:

to fast three days every month, to pray two <i>rak'as</i> in the forenoon, and to observe a <i>witr</i> before going to sleep.” *i.e. the Prophet. (Bukhari and Muslim.)

وَعَنْ أَبِي هُرَيْرَةَ رَضِيَ اللَّهُ عَنْهُ قَالَ: أَوْصَانِي خَلِيلِي بِثَلَاثٍ: صِيَامِ ثَلَاثَةِ أَيَّام من كل شهر وركعتي الضُّحَى وَأَن أوتر قبل أَن أَنَام

References1 variant
In-Book Reference
Book 4, Hadith 677