Making up for Missed Fasts comes first.

Question

Whoever has to make up for days of fasting from Ramadhan, and he desires to fast the six days from Shawwal, and he wants to fast them before making up for what is due on him. He wants to do this due to the consideration that the days of Ramadhan can be made up for at any time, but the six days of Shawwal are only in the month of Shawwal. I hope for some benefit from you, and may Allah reward you.


Answer

What is legislated is that the person begins with making up for the fast before fasting the six days. This is because the Messenger (Sallallahu Alayhi wa Sallam) said:

"Whoever fasts Ramadhan, and then follows it up with six (days of fasting) from Shawwal, then that is as if he fasted the entire time (i.e. year) (Muslim no 1164)

If he fasts it before making up for the missed fasts, he has not achieved following up Ramadhan with it. Rather, he has fasted it before the other part of it (i.e., completing Ramadhan). This is also because the obligation is more important and it has more right to be given precedence.



Shaikh Ibn Baz (Rahimahullah)

Reference: Fatawa Islamiyah Volume 3 Pages 337-338