Can we combine intention for our missed fard fasts with nafil fasts (like 9 days of Dhul Hijjah, Monday, Thursday, ashura, the three white days of each month). So as to get a double reward for the fardh as well as the nafil.
Please explain in detail. May Allah reward you with goodness.
Shaikh Ibn Al-Uthaymin said that you can take the intention of compensating the missed days of Ramadan by fasting the Sunnah days of Monday and Thursday and the three white days, also you can fast the 9 days of Dhul Hijjah, with the intention of compensating Ramadan missed days, since compensating your fast is a great act of worship.
As for the reward Shaikh Al-Albani said that you take the reward of one act (compensation) with the multiplication by 10 or more and you take only one reward of good intention but without multiplication for the second intention which is fasting on that superior or Sunnah day.
As for Arafa day 9th of Dhul Hijjah, you need to fast it as a Nafilah and not compensation as there is a scholar difference in opinion regarding combining intentions in fasting this day. So be on the safe side.