Tafsir of At-Tawbah 9:125

وأما الذين في قلوبهم مرض فزادتهم رجسا إلى رجسهم

But as for those in whose hearts is a disease, it will add Rijs to their Rijs. The Surah increases them in doubt, and brings more suspicion on top of the doubts and suspicion that they had before. Allah said in another Ayah,

وننزل من القرءان ما هو شفاء

And We send down in the Qur'an that which is a healing. (17:82) and,

قل هو للذين ءامنوا هدى وشفاء والذين ﻻ يومنون فى ءاذانهم وقر وهو عليهم عمى أوليك ينادون من مكان بعيد

Say: "It is for those who believe, a guide and a healing. And as for those who disbelieve, there is heaviness (deafness) in their ears, and it (the Qur'an) is blindness for them. They are those who are called from a place far away (so they neither listen nor understand).'' (41:44) This indicates the misery of the hypocrites and disbelievers, since, what should bring guidance to their hearts is instead a cause of misguidance and destruction for them. Similarly, those who get upset by a type of food, for instance, will be upset and anxious even more if they are fed that food!

وماتوا وهم كافرون

and they die while they are disbelievers