What is the virtue of fasting the first fifteen days of Sha’ban, and what is the ruling on fasting them and forsaking the fasting of Mondays and Thursdays for the remainder of the month for one who is accustomed to fasting them?

There is no specific virtue reported for fasting the first half of Sha'ban, but the Prophet, peace and blessings be upon him, generally fasted a great deal in Sha'ban. As for the hadith prohibiting fasting after mid-Sha'ban, "When Sha'ban is halfway through, do not fast," scholars have differed regarding its authenticity. Those who considered it good (hasan) or authentic reconciled it with the hadiths that indicate the permissibility of fasting in Sha'ban by explaining that the prohibition applies to those who do not have a regular habit of fasting, or those who specifically fast only in the second half. Ibn al-Qayyim held that the prohibition specifically applies to intentionally fasting after the middle of the month without a regular habit or without connecting it to the first half. And whoever is accustomed to fasting on Mondays and Thursdays should not abandon their fasting in the second half of Sha'ban.