Where two hamzahs meet, the first is vowelled and the second sākin, the second is replaced by a sound corresponding to the first hamzah’s vowel.
Think of fatḥah with alif, kasrah with yāʾ and ḍammah with wāw. Apply the rule after identifying the two hamzahs and their states, not merely from the word’s appearance.
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Vowelled then sākin hamzah
Rules of Hamzah — Taḥqīq, Tashīl, Ibdāl and Hamzat al-Waṣl
Where two hamzahs meet, the first is vowelled and the second sākin, the second is replaced by a sound corresponding to the first hamzah’s vowel.
Think of fatḥah with alif, kasrah with yāʾ and ḍammah with wāw. Apply the rule after identifying the two hamzahs and their states, not merely from the word’s appearance.