Question: I heard knowledge seekers saying that it is not valid to combineobserving Sawm (Fast) on Monday and Thursday and the White Days (13th, 14th, and 15th of every Hijri month). Rather, one should observe Sawm of either one of them. Is this correct? If so, why?
Answer: What you heard regarding the invalidity of combining the Sawm of Monday and Thursday and the White Days is incorrect. It is Mustahab (desirable) to observe Sawm on these days because there are proofs urging the observation of their Sawm… read more here.