The Messenger of Allah ﷺ used to fast so much that we would say he never broke his fast, and he would refrain from fasting so much that we would say he never fasted. I never saw the Messenger of Allah ﷺ fast more in any month than he did in Shaban.
أخبرنا الربيع بن سليمان بن داود قال حدثنا ابن وهب قال أخبرني مالك وعمرو بن الحارث وذكر آخر قبلهما أن أبا النضر حدثهم عن أبي سلمة
كان رسول الله ﷺ يصوم حتى نقول ما يفطر ويفطر حتى نقول ما يصوم وما رأيت رسول الله ﷺ في شهر أكثر صياما منه في شعبان
Bukhari transmitted it in the Book of Fasting, chapter on fasting in Shaban, no. 1969, and Muslim in the Book of Fasting, chapter on the Prophet's ﷺ fasting in months other than Ramadan, no. 115/1156, from the hadith of Malik through this same chain, and it is also in Kubra, no. 2660, and in Muwatta, 1/309. Abu Nadr is the freedman of Umar bin Ubaydullah, and there is another narrator before them, I think it is Ibn Lahia.