In الْمُسْتَقِيمَ, mīm is a moon letter, so the article lām is pronounced. The qāf with kasrah retains its istiʿlāʾ nature; do not change it into kāf, while avoiding excessive heaviness.
When pausing at the final mīm, the preceding madd yāʾ gives madd ʿāriḍ li-s-sukūn. It is not madd lāzim, because the relevant final sukūn comes from pausing.
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Al-mustaqīm: qāf with kasrah and pausal madd
Al-Fātiḥah: Integrated Tajwīd, Madd and Pausing Practice
In الْمُسْتَقِيمَ, mīm is a moon letter, so the article lām is pronounced. The qāf with kasrah retains its istiʿlāʾ nature; do not change it into kāf, while avoiding excessive heaviness.
When pausing at the final mīm, the preceding madd yāʾ gives madd ʿāriḍ li-s-sukūn. It is not madd lāzim, because the relevant final sukūn comes from pausing.