What is the ruling on the prayer of a person with diminished intellect who cannot distinguish between the prayers?

Question : The questioner, Muhammad Sudani, who resides in Riyadh, says in this question: We have a young man who is thirty-five years old and has a deficiency in his intellect. He constantly prays the obligatory and voluntary prayers, but he does not know how to distinguish between them. For example, he prays two rak'ahs for the Fajr prayer, then prays four, or three, or five. The same is the case for all the other times. He does not know how to perform wudu'; he washes his hands before his face, for instance. He memorizes Surat al-Fatihah but leaves out the verses. He recites three surahs in one rak'ah, all of them either whispered or aloud. We gathered with him, but that did not benefit him. In this state, he consistently maintains the prayers in the mosque, and he is the first to go to the mosque on Friday. The question is: Is this man's prayer considered valid according to his intellect, or not? And is it permissible for us to encourage him to continue in this state that I described, or should we forbid him from it? May Allah reward you with good.

Answer : This is, in reality, like a child. Like a child who distinguishes right from wrong, or even less than that. So, we accept what he has achieved and do not demand from him what he has not achieved. In other words, we enable him to pray according to his condition, or enable him to go to the mosque according to his condition, provided that he does not cause harm to the mosque or to the worshippers. However, we do not demand the obligatory from him, because this person is, in reality, deprived of intellect; his intellect is like that of a child who distinguishes right from wrong, or less. Yes.