One of the great mysteries of the Quranic reading traditions are their many phonetic irregularities, that seem to have no purpose except to show off some grammatical oddity. One of these is the ʾimālah of al-kēfīrīna. Ibn Ḫālawayh in his Ḥuǧǧah has an interesting discussion. 🧵

The plural of 'disbelievers', besides the now popular kuffār, is also kāfirūna in the Quran. In the genitive and accusative this becomes kāfirīna. Some readers read this (and ONLY this) as kēfirīna.
This is the reading of: ʾAbū ʿAmr, al-Dūrī ← al-Kisāʾī and Ruways ← Yaʿqūb.

In his al-Ḥuǧǧah fī l-Qirāʾāt al-Sabʿ, Ibn Ḫālawayh sets out to rationalize and explain the practices of the seven readers canonized by his teacher, Ibn Mujāhid. He also discusses al-Kēfirīna. Let's translate and give commentary along the way.

"As for the saying of the almighty 'wa-ḷḷāhu muḥīṭun bi-l-kāfirīna'", al-kāfirīna is read with ʾimālah or without ʾimālah whenever it is in the accusative or genitive.

So the explanation is that it is because of the meeting of four kasras within a single word"

"It is the kasrah of the fāʾ, rāʾ and yāʾ -- and the rāʾ can carry two kasras, so they pull the ʾalif, because it is quiscentent, by their strength, so they cause ʾimālah to apply to it".

So lots to unpack here. Where on earth is he getting four kasrahs from?!