My friend (i.e. the Prophet) instructed me to observe three practices which I never leave: he instructed me to fast three days every month, and not to sleep but after observing the witr, and to observe supererogatory prayer in the forenoon while traveling and while resident. (Using translation from Abū Dāʾūd 1433)
أَوْصَانِي خَلِيلِي ﷺ بِثَلَاثٍ لَا أَدَعُهُنَّ لِشَيْءٍ أَوْصَانِي بِصِيَامِ ثَلَاثَةِ أَيَّامٍ مِنْ كُلِّ شَهْرٍ وَأَنْ لَا أَنَامَ إِلَّا عَلَى وَتْرٍ وَسُبْحَةِ الضُّحَى فِي الْحَضَرِوَالسَّفَرِ