Ustadh,if I still have Ramadan fasts to make up due to illness ,can I fast Arafah with the intention of Arafah and make up the missed Ramadan fasts after ?

This is one of the most common questions in regards to making up a fast when there is an occasion for a voluntary fast coming up, such as Arafah or the six days of Shawwal. The rule is that your intention should always be to make up the obligatory fasts. You ask Allah (subhanahu wa ta'ala) from His bounty—and His bounty is expansive—whether you get the double reward or not. By double reward, I mean the reward of making up the fast as well as it being on the day of Arafah. However, your intention should specifically be for making up the fast so that you do not fall into the different views of the people of Ilm (knowledge). Some of the people of Ilm have said that your fasting is invalid if you intend something other than making them up.