That the Prophet would not fast any month of the year in full except Shaban and he used to join it to Ramadan. (Using translation from Nasāʾī 2353)
عَنِ النَّبِيِّ ﷺ أَنَّهُ لَمْ يَكُنْ يَصُومُ مِنَ السَّنَةِ شَهْرًا تَامًّا يُعْلَمُ إِلَّا شَعْبَانَ يَصِلُ بِهِ رَمَضَانَ