Which is better: fasting three days every month or fasting on Mondays and Thursdays? What are the relevant Hadiths regarding this, and should the three days be the 13th, 14th, and 15th of the month?

Fasting on Mondays and Thursdays is better than fasting three days a month, because whoever fasts them every week has fasted eight days monthly, thereby combining the virtue of fasting on Mondays and Thursdays with fasting three days a month. It is preferable for the three white days to be the thirteenth, fourteenth, and fifteenth of the lunar month, but it is permissible to fast them at any time of the month, whether separately or consecutively.

The virtue of fasting on Mondays and Thursdays: It is the day the Prophet (peace be upon him) was born and revelation descended upon him, and deeds are presented on these days. The Prophet used to seek to fast them.

The virtue of fasting three days a month: The Prophet (peace be upon him) recommended it, and it is equivalent to fasting a lifetime.