What is the precise intention (niyyah) for making up missed fasts by fasting like Prophet Dawud (peace be upon him), along with the intention of counting any excess as a supererogatory act (sunnah), and is it permissible to observe recommended fasts, such as Arafah and Ashura, if they coincide with a day of breaking the fast (Yawm al-Fitr) in the context of fasting like Prophet Dawud?

If someone needs to make up for missed fasts but doesn't know the exact number, they should strive to estimate the days and make up what they are certain will absolve them, according to the Shafi'i and Hanbali schools. Alternatively, they should make up what they predominantly believe, according to the Hanafi and Maliki schools. The intention resides in the heart and does not require verbalization; indeed, verbalizing it is an innovation. If a day for making up a fast coincides with a recommended day for fasting, one should fast it with the intention of making up the missed fast, not as a voluntary fast. It is disliked by the majority of scholars for someone who owes missed fasts to observe voluntary fasts before making up the obligatory ones, whereas the Hanafis permit it without any dislike.