würde ich mal instinktiv sagen ...

Also so à la he renounced his faith?

He renounced his faith.

renounce - disavow - abandon - context would help

Kontext:
Sie blieb ihrem Glauben lange Zeit treu.
Mit 50 jedoch, schwor sie ihm ab.

looks like abandon to me

schau mal hier: Siehe Wörterbuch: apostat*

... in the special context of historical wars involving Christianity and accusations of heresy, if this is still about Huguenots and so on.

'Renounce one's faith' is of course also possible; to recant in the religious sense is to renounce one's faith.

'Apostate' is normally a noun (or an adjective); I wouldn't recommend trying 'apostatize,' which is very technical and uncommon. (And it's unclear, to me at least, whether it also, or even primarily, means to cause someone to become an apostate.)

That is, 'recant' only works if the renunciation is forced, as by threat of burning: After being tortured by the Inquisition, many so-called heretics recanted.