Is prayer obligatory for someone whose hearing has become heavy, so he pronounces letters incorrectly due to his inability to hear words?

Religious obligations, such as prayer, are not lifted from someone with impaired hearing if they comprehend the matters of Islam and prayer. The juristic principle dictates that one should perform what they are able to, and what they are unable to do is waived, based on the Almighty’s saying: ﴿So fear Allah as much as you are able.﴾ Therefore, if one is unable to recite during prayer, or unable to recite certain parts, due to impaired hearing or an inability to learn, prayer is not waived for them. They must pray and recite what they have mastered from the Quranic verses, even if they cannot pronounce some letters perfectly due to their disability. If they are completely unable to recite, their prayer is valid, and they should engage in the remembrance of Allah instead of recitation.