ذِكْرُ خَبَرٍ ثَانٍ يُصَرِّحُ بِالْإِيمَاءِ الَّذِي أَشَرْنَا إِلَيْهِ
Messenger of Allah ﷺ used to fast till one would say that he would never stop fasting, and he would abandon fasting till one would say that he would never fast. I never saw Messenger of Allah ﷺ fasting for a whole month except the month of Ramadan, and did not see him fasting in any month more than in the month of Sha'ban. (Using translation from Bukhārī 1969)
«كَانَ رَسُولُ اللَّهِ ﷺ يَصُومُ حَتَّى نَقُولَ لَا يُفْطِرُ وَيُفْطِرُ حَتَّى نَقُولَ لَا يَصُومُ وَمَا رَأَيْتُ رَسُولَ اللَّهِ ﷺ اسْتَكْمَلَ صِيَامَ شَهْرٍ قَطُّ إِلَّا رَمَضَانَ وَمَا رَأَيْتُهُ أَكْثَرَ صِيَامًا مِنْهُ فِي شَعْبَانَ»