❖ Question:
If one combines the intention of a nafl fast and a make-up fast of Ramadan, will he receive the reward of both?
Source: Fatāwā Amunpuri by Shaykh Ghulam Mustafa Zaheer Amunpuri
✿ Answer:
Combining the intention of both is not correct. The intention must be kept pure. If one intends to fast for making up a missed day of Ramadan, the obligation will be fulfilled. However, if he mixes it with the intention of nafl (voluntary) fasting, the fulfillment of the obligatory fast becomes doubtful.
❀ Statement of Imām al-Nawawī رحمه الله:
لَا تَجُوزُ النِّيَّةُ الْمُشْتَرَكَةُ بَيْنَ الْفَرْضِ وَالنَّفْلِ
"A combined intention between an obligatory fast and a voluntary fast is not permissible."
(al-Majmūʿ Sharḥ al-Muhadhdhab: 6/374)

① One cannot combine the intention of Ramadan make-up fasts with nafl fasts.
② Only the obligatory fast will count if the intention is for Ramadan qaḍāʾ.
③ Adding a nafl intention invalidates the purity of the obligation.