During final settlement after promising, last salary deducted.

HI lawyer, I served for a firm for more than 8 years and during Feb this year my health was deteriorated for which doctor told me to take three weeks rest which was rejected by our firm. Due to the pressure from my department people i already submitted resignation. Previous to resignation i was on leave for about four weeks. When i came back the personnel pressure was more for which i submitted resignation. They accepted my resignation and relieved on the same day telling me that everything will be paid without deduction, but they deducted my last salary. Please clarify should they pay.