In بِسْمِ اللَّهِ, the mīm before the Divine Name bears kasrah, so the lām in Allāh is pronounced lightly. This is determined by the preceding vowel, not by the sacred status of the word.
Compare قَالَ اللَّهُ, where preceding fatḥah makes the lām heavy, with بِاللَّهِ, where it is light. Identify the trigger before practising the sound.
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Basmalah: the lām in Allāh
Al-Fātiḥah: Integrated Tajwīd, Madd and Pausing Practice
In بِسْمِ اللَّهِ, the mīm before the Divine Name bears kasrah, so the lām in Allāh is pronounced lightly. This is determined by the preceding vowel, not by the sacred status of the word.
Compare قَالَ اللَّهُ, where preceding fatḥah makes the lām heavy, with بِاللَّهِ, where it is light. Identify the trigger before practising the sound.