Allah's Messenger (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 Allah's Messenger (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.
Sahih al-Bukhari Book 30, Hadith 76
← Previous Hadith The Prophet (ﷺ) made a bond of brotherhood between Salman and Abu Ad-Darda.' Salman paid a visit to Abu Ad-Darda' and found Um Ad-Darda' dressed in shabby clothes and asked her why she was in that state. She replied, "Your brother Abu Ad-Darda' is not interested in (the luxuries of) this world." In the meantime Abu Ad-Darda' came and prepared a meal for Salman. Salman requested Abu Ad- Darda' to eat (with him), but Abu Ad-Darda' said, "I am fasting." Salman said, "I am not going to eat unless you eat." So, Abu Ad-Darda' ate (with Salman). When it was night and (a part of the night passed), Abu Ad-Darda' got up (to offer the night prayer), but Salman told him to sleep and Abu Ad- Darda' slept. After sometime Abu Ad-Darda' again got up but Salman told him to sleep. When it was the last hours of the night, Salman told him to get up then, and both of them offered the prayer. Salman told Abu Ad-Darda', "Your Lord has a right on you, your soul has a right on you, and your family has a right on you; so you should give the rights of all those who has a right on you." Abu Ad- Darda' came to the Prophet (ﷺ) and narrated the whole story. The Prophet (ﷺ) said, "Salman has spoken the truth."

Sahih al-Bukhari Book 30, Hadith 75 Next Hadith → The Prophet (ﷺ) never fasted in any month more than in the month of Sha'ban. He used to say, "Do those deeds which you can do easily, as Allah will not get tired (of giving rewards) till you get bored and tired (of performing religious deeds)." The most beloved prayer to the Prophet (ﷺ) was the one that was done regularly (throughout the life) even if it were little. And whenever the Prophet (ﷺ) offered a prayer he used to offer it regularly .

Sahih al-Bukhari Book 30, Hadith 77