Q: Does oversleep during Ramadan day spoil our fast?
In the name of God, praise be to Him, and peace be upon his Messenger.
Ramadan is a month of worship by night and day. Night worship includes observing Tarawih prayer and reciting the Qur’an; whereas day worship comprises mainly fasting, in addition, of course, to the usual prayers. Therefore, there is nothing wrong with the very fasting of an individual even though s/he spends the whole day sleeping provided that s/he performs their set daytime prayers each in its due time.
Sleep might even prevent the observer of the fast from getting involved into some improper acts which run counter to the reason for which fasting was meant and which might ultimately spoil it. Such fast-damaging acts are lying, backbiting, testifying to falsehood, and so forth.
However, fasting is meant to make believers feel the pain of hunger and thirst and try their resistance to other bodily calls. For this reason, oversleep during a Ramadan day ought to be given up. The observer of fast who gets up just for prayer and then goes back to sleep misses a great amount of good. S/he ought to keep themselves busy praying, reciting the Qur’an, praising the Lord and invoking Him so that they would add other acts of worship to the act of fasting.