In فَمَنْ يَعْمَلْ and وَمَنْ يَعْمَلْ, sākin nūn meets yāʾ across a word boundary. Yāʾ is in «يَنْمُو», so the rule is idghām with ghunnah.
This is assimilation, not simply an isolated nasal sound. Compare:
مَنْ يَعْمَلْ — idghām with ghunnah.
مَنْ خَفَّتْ — throat-letter iẓhār.
مَنْ ثَقُلَتْ — ikhfāʾ before thāʾ.
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Idghām with ghunnah before yāʾ
Al-Qāriʿah and Az-Zalzalah — Comparative Tajwīd Practice
In فَمَنْ يَعْمَلْ and وَمَنْ يَعْمَلْ, sākin nūn meets yāʾ across a word boundary. Yāʾ is in «يَنْمُو», so the rule is idghām with ghunnah.
This is assimilation, not simply an isolated nasal sound. Compare:
مَنْ يَعْمَلْ — idghām with ghunnah.
مَنْ خَفَّتْ — throat-letter iẓhār.
مَنْ ثَقُلَتْ — ikhfāʾ before thāʾ.