لَتَرَوُنَّ ends in a doubled nūn: ghunnah is required. The written wāw before it is vowelled here, so it must not be classified as a madd wāw merely because of its shape.
In الْجَحِيمَ, lām is pronounced before jīm; «حِي» is natural madd. At a pause on verse 6, the final mīm becomes sākin after that madd letter, creating madd ʿāriḍ.
Keep the nūn-ghunnah and verse-final madd as separate principles.
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Two distinct rulings in la-tarawunna-l-jaḥīm
Al-ʿAṣr and At-Takāthur: Applied Ghunnah, Madd, Lām and Waqf
لَتَرَوُنَّ ends in a doubled nūn: ghunnah is required. The written wāw before it is vowelled here, so it must not be classified as a madd wāw merely because of its shape.
In الْجَحِيمَ, lām is pronounced before jīm; «حِي» is natural madd. At a pause on verse 6, the final mīm becomes sākin after that madd letter, creating madd ʿāriḍ.
Keep the nūn-ghunnah and verse-final madd as separate principles.