What is the ruling on the prayer of a person who converted to Islam secretly?

Primary text

As for his personal prayer, the matter is between him and Allah Almighty. If it is known that he had embraced Islam, then performed ablution, and prayed with a correct intention, his prayer is valid. If not, he must repeat the prayer because ablution is not valid for an infidel. If he did not embrace Islam before the prayer, he was in a state of being a non-Muslim and ritually impure when beginning it, so it is not valid from him.