The criterion of silent recitation in the prayer is that one hears oneself

Question

If a person does not recite in the prayer loudly enough to hear himself, will the prayer be valid or not? What is the position on which fatwa is given (mufta bihi)?

Answer

The most cautious course (ahwat) is to recite loudly enough that one can hear oneself; however, there is no repeating (i‘ada) of past prayers.

Source: Fatawa Mahmudiyya

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