He Left Islam, But Later Accepted Islam
Question :
If a Muslim perpetrates a deed that takes him outside of the fold of Islam, a deed that makes him an apostate, and if he then repents to Allâh Almighty, does he deserve the punishment of the apostate (i.e., death) or is his repentance enough? And what if he lives in a country that doesn't apply the Shari'ah?
Answer:
If a person leaves Islam but then returns to it repenting, it is not permissible to punish him, because the punishment for apostasy is for a person who persists in his disbelief and refuses to return to Islam. But when a person repents, his repentance nullifies all that comes before it as is proved by the Book and the Sunnah.
And with Allâh is the facilitation to do what is right. May Allah send peace and blessings upon Muhammad, his family, and his Companions.
Source:
The Permanent Committee
Fatawa Islamiyah, Vol. 7 Page 259