All three verbs are hollow, yet their imperfect patterns are not identical.
قَالَ — يَقُولُ: ḍammah on qāf, wāw retained; command قُلْ.
بَاعَ — يَبِيعُ: kasrah on bāʾ, yāʾ retained; command بِعْ.
خَافَ — يَخَافُ: fatḥah on khāʾ, alif in the imperfect; command خَفْ.
Iʿlāl rules work together with root identity and the underlying pattern. There is no single interchangeable vowel template for every hollow verb.
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Why the Three Imperfect Patterns Differ
Hollow Verbs: Seven Iʿlāl Rules and Three Short Paradigms
All three verbs are hollow, yet their imperfect patterns are not identical.
قَالَ — يَقُولُ: ḍammah on qāf, wāw retained; command قُلْ.
بَاعَ — يَبِيعُ: kasrah on bāʾ, yāʾ retained; command بِعْ.
خَافَ — يَخَافُ: fatḥah on khāʾ, alif in the imperfect; command خَفْ.
Iʿlāl rules work together with root identity and the underlying pattern. There is no single interchangeable vowel template for every hollow verb.