"The Messenger of Allah used to fast three days in the middle of every month, and he rarely did not fast on Friday." (Using translation from Nasāʾī 2368)
أَنَّ رَسُولَ اللهِ ﷺ «كَانَ يَصُومُ ثَلَاثَةَ أَيَّامٍ مِنْ كُلِّ شَهْرٍ وَقَلَّمَا رَأَيْتُهُ يُفْطِرُ يَوْمَ الْجُمُعَةِ»