If a fasting person commits apostasy but reverts to Islam during the same day, is his fast valid?

All perfect praise be to Allaah, the Lord of the worlds. I testify that there is none worthy of worship except Allaah and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.

The fasting of such a person is invalid, and he is required to make up for that day, since the fast became invalid on account of apostasy. Allaah says (what means): {…And whoever denies the faith—his work has become worthless, and he, in the Hereafter, will be among the losers.} [Quran 5: 5] Also, fasting is an act of worship that requires intention, and the intention of fasting is invalidated by apostasy. If the person in question returned to Islam during the same day, then he would have to keep fasting for the rest of the day since there was no valid excuse to break his fast.

Allaah Knows best.