The source warns against over-emphasizing emphatic letters until a single consonant sounds doubled, a fatḥah resembles ḍammah, or a following alif sounds like wāw. Those are pronunciation distortions, not proper tafkhīm.
For instance, طَالَ needs a full emphatic quality without replacing its long ā with something resembling ū. Preserve both the letter and the vowel.
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Tafkhīm must not distort the consonant
Tafkhīm and Tarqīq — Alif, Divine-Name Lām and Rāʾ
The source warns against over-emphasizing emphatic letters until a single consonant sounds doubled, a fatḥah resembles ḍammah, or a following alif sounds like wāw. Those are pronunciation distortions, not proper tafkhīm.
For instance, طَالَ needs a full emphatic quality without replacing its long ā with something resembling ū. Preserve both the letter and the vowel.