A person should say his prayer correctly...

A person should say his prayer correctly, and if one cannot by any means recite the whole of Surat-ul-Hamd, he should recite it as he can provided that the part pronounced correctly is considerable ; but if that is a very small part, then as an obligatory precaution, he should add to it some verses of Qur'an which he can recite correctly. And if he cannot do that, he should add some Tasbih to it. But if someone cannot recite al-Hamd correctly at all, then there is no necessary replacement for it.

If a person does not utter a certain word of al-Hamd or the other Surah intentionally or while he is negligently ignorant, or utters one letter for another, like Z for D, or changes the inflections, by adding a vowel kike A or I where not needed or changing their pronunciations in such a manner that the word is considered as incorrect, or does not render Tashdid (pronouncing the letter hard as if there is two letters) properly, his prayer is void.

If a person has learnt a word which he believes to be correct, and recites it that way in prayers, but comes to know…