Surah Al-Waqi'ah 56:22

وَحُورٌ عِينٌ

And [for them are] fair women with large, [beautiful] eyes,

Translation: Saheeh International

Tafsir

and houris maidens with intensely black eyes set against the whiteness of their irises with wide eyes ‘īn the ‘ayn here is inflected with a kasra instead of a damma because it the kasra better harmonises with the yā’; the singular is ‘aynā’ similar in pattern to hamrā’; …

Excerpt from Tafsir al-Jalalayn, commentary on 56:22, via Quran.com. The reader has the full commentary and 9 more tafsirs.