such as substituting the rāʾ with a lām—making the rāʾ into a lām—so that he says, “al-ḥamdu lillāhi labbi al-ʿālamīn.” Such a person is unlettered, because he has replaced a letter of al-Fātiḥah with another letter.

An exception to this issue is pronouncing the ḍād as a ẓāʾ. According to the stronger view—and it is the position of the school of law—this is excused, because the distinction between the two is subtle, especially for a layperson. A layperson can scarcely distinguish between the ḍād and the ẓāʾ. Thus, if he says, “ghayri al-maghẓūbi ʿalayhim wa lā al-ẓāllīn,” he has replaced the ḍād with a ẓāʾ. This is excused because of the difficulty of avoiding it and of distinguishing between the two, especially for ordinary people.

Thus, substitution falls into the following categories:

1. Substituting one letter for another that is not similar to it: such a person is unlettered.
2. Substituting a letter with one close to it, such as pronouncing the ḍād as a ẓāʾ: this is excused.
3. Pronouncing the ṣād as a sīn, such as saying “al-sirāṭ” instead of “al-ṣirāṭ”: this is permissible. Rather, one should recite it this way on occasion, because it is one of the seven canonical recitations. A person should occasionally recite according to the seven canonical recitations, but on condition that he does not do so before the general public. For if you recited before them in a manner unfamiliar to them, they would object to it and become confused.

OR HE MAKES A GRAMMATICAL ERROR IN IT THAT CHANGES THE MEANING ..........

His statement, “or he makes a grammatical error in it that changes the meaning,” means that he makes, in al-Fātiḥah, a grammatical error that changes the meaning.

A grammatical error is a change in the vowel endings, whether it is a morphological or syntactical change. If it changes the meaning, then the one who makes that change is unlettered; but if it does not change it