"The Messenger of Allah enjoyed three things upon me: To sleep after praying Witr, to perform Ghusal on Friday, and to fast three days of each month." (Sahih).
أَمَرَنِي رَسُولُ اللَّهِ ﷺ بِثَلاَثٍ بِنَوْمٍ عَلَى وِتْرٍ وَالْغُسْلِ يَوْمَ الْجُمُعَةِ وَصَوْمِ ثَلاَثَةِ أَيَّامٍ مِنْ كُلِّ شَهْرٍ