Another useful clue appears after وَ or فَ: Lam al-Amr becomes sakin, while Lam Kay retains its kasrah.
وَلِيَسْمَعُوا — and so that they may listen: لامِ کَی.
وَلْيَسْمَعُوا — and they should listen: لامِ امر.
Compare: فَلْيَكْتُبْ زَيْدٌ — then let Zayd write. The lām after فَ is sakin.
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Another useful clue appears after وَ or فَ: Lam al-Amr becomes sakin, while Lam Kay retains its kasrah.
وَلِيَسْمَعُوا — and so that they may listen: لامِ کَی.
وَلْيَسْمَعُوا — and they should listen: لامِ امر.
Compare: فَلْيَكْتُبْ زَيْدٌ — then let Zayd write. The lām after فَ is sakin.