Query: Is there a punishment for apostasy? If so, what is it and why?
Some Islamic jurists are of the opinion that the apostate should be punished if he’s insistent. The details of such punishment are controversial among Muslim scholars and Islamic schools of thought. However, there are inevitable penalties incurred; such as separating between him and his wife; and deprivation of inheriting his Muslim relatives or being inherited by them until declared innocent with a judicial sentence.
These penalties are imposed because Islam doesn’t compel anyone to convert to Islam: Allah (Glory be to Him) says in the Glorious Qur’an: “There’s no compulsion in religion”. (2: 256) In addition, Islam asked people to use their minds and consider everything before converting to Islam. Thus, if they converted to Islam of their own free will, they should abide by the rules thereof. Allah knows best.
Sources: Al-Azhar Al-Sharif