In الصِّرَاطَ, the article lām assimilates into ṣād, a sun letter. Ṣād remains emphatic even under kasrah because it is an istiʿlāʾ letter; it must not become plain sīn.
Rāʾ bears fatḥah and is heavy, while ṭāʾ is likewise emphatic. Tafkhīm does not mean exaggerating every heavy consonant equally; preserve each letter's own articulation and quality.
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Aṣ-ṣirāṭ: heavy letters and article assimilation
Al-Fātiḥah: Integrated Tajwīd, Madd and Pausing Practice
In الصِّرَاطَ, the article lām assimilates into ṣād, a sun letter. Ṣād remains emphatic even under kasrah because it is an istiʿlāʾ letter; it must not become plain sīn.
Rāʾ bears fatḥah and is heavy, while ṭāʾ is likewise emphatic. Tafkhīm does not mean exaggerating every heavy consonant equally; preserve each letter's own articulation and quality.