"The Messenger of Allah took a covenant from me for three: To not sleep except after performing Witr, to fast three days of every month, and to perform the Duha prayer." (Using translation from Tirmidhī 760)
عَهِدَ إِلَيَّ النَّبِيُّ ﷺ فِي ثَلَاثٍ لَا أَدَعُهُنَّ أَبَدًا لَا أَنَامُ إِلَّا عَلَى وِتْرٍ وَفِي صَلَاةِ الضُّحَى وَصِيَامِ ثَلَاثَةِ أَيَّامٍ مِنْ كُلِّ شَهْرٍ