Usama bin Zayd reported,

The Messenger of Allah ﷺ used to fast days continuously until it would be said that he never broke his fast, and he would go without fasting for stretches of days until it seemed he would scarcely fast at all, except for two days of the week. If those two days fell within his fasting, fine, otherwise he would fast them. And he did not fast in any month as much as he fasted in Shaban.I said, "Messenger of Allah, you fast until it seems you will never break your fast, and you go without fasting until it seems you will hardly fast at all, except for two days that you always fast if they fall within your fasting period."He asked, "Which two days?"I said, "Monday and Thursday."He said, "Those are two days on which deeds are presented to the Lord of the Worlds, and I love that my deeds be presented while I am fasting."I said, "And I have not seen you fast in any month as much as you fast in Shaban."He said, "That is a month people overlook, between Rajab and Ramadan. It is a month in which deeds are raised up to the Lord of the Worlds, and I love that my deeds be raised up while I am fasting."

عن أسامة بن زيد، قال

كان رسول الله ﷺ يصوم الأيام يسرد حتى يقال: لا يفطر، ويفطر الأيام حتى لا يكاد أن يصوم إلا يومين من الجمعة، إن كان في صيامه، وإلا صامهما، ولم يكن يصوم من شهر من الشهور ما يصوم من شعبان، فقلت: يا رسول الله، إنك تصوم لا تكاد أن تفطر، وتفطر حتى لا تكاد أن تصوم إلا تصوم إلا يومين إن دخلا في صيامك إلا صمتهما! قال: أي يومين؟ قال: قلت: يوم الاثنين ويوم الخميس. قال: ذانك يومان تعرض فيهما الأعمال على رب العالمين، وأحب أن يعرض عملي وأنا صائم. قال: قلت: ولم أرك تصوم من شهر من الشهور ما تصوم من شعبان! قال: ذاك شهر يغفل الناس عنه بين رجب ورمضان، وهو شهر ترفع فيه الأعمال إلى رب العالمين، فأحب أن يرفع عملي وأنا صائم.