عَنْ عَائِشَةَ قَالَتْ: كَانَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ يَصُومُ حَتَّى نَقُولَ: لَا يُفْطِرُ وَيُفْطِرُ حَتَّى نَقُولَ: لَا يَصُومُ وَمَا رَأَيْتُ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ اسْتكْمل صِيَام شهر قطّ إِلَّا رَمَضَانَ وَمَا رَأَيْتُهُ فِي شَهْرٍ أَكْثَرَ مِنْهُ صِيَامًا فِي شَعْبَانَ وَفِي رِوَايَةٍ قَالَتْ: كَانَ يَصُوم شعْبَان كُله وَكن يَصُوم شعْبَان إِلَّا قَلِيلا

He said that when God’s messenger was asked about fasting on Monday he said, “On it I was born and on it the revelation was first sent down to me.”* *The meaning seems to be that as this day is so distinguished, one could not choose a better one.Muslim transmitted it.