Shaykh Abdul-Kareem al-Khudair, hafidahullah, said:

“… Some people could only fast one day of the week. So is fasting Monday better than fasting Thursday [for him] or is Thursday better? Yes, fasting on Monday is better than fasting on Thursday. More hadiths have come concerning Monday. With that being said, if it easy for him to fast both days, that is more preferable or else if he can’t fast except one day out of the two days, then with no doubt Monday is better and more hadiths have come regarding it… “. End. [Reference]

Translated by

AbdulFattaah Bin Uthman
Abu Fajr