In «الشِّتَاءِ», shīn is a sun letter; article lām assimilates and shīn is doubled. Separately, a madd alif is followed by hamzah within the same word, producing madd muttaṣil.
These two rules have different triggers. In «وَالصَّيْفِ», ṣād likewise assimilates the article lām, but its yāʾ follows fatḥah and is a līn yāʾ, not a madd meeting hamzah. Do not apply the same lengthening to both words.
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Ash-shitāʾ: sun-letter assimilation and connected madd
Al-Fīl and Quraysh: Applied Iẓhār, Ikhfāʾ, Idghām, Madd and Waqf
In «الشِّتَاءِ», shīn is a sun letter; article lām assimilates and shīn is doubled. Separately, a madd alif is followed by hamzah within the same word, producing madd muttaṣil.
These two rules have different triggers. In «وَالصَّيْفِ», ṣād likewise assimilates the article lām, but its yāʾ follows fatḥah and is a līn yāʾ, not a madd meeting hamzah. Do not apply the same lengthening to both words.