Tafsir of Al-Waqi'ah 56:23

Meaning: in clarity. It is qualified by "the stored" (al-maknun), meaning that which is concealed by what protects it, because it is clearer and further removed from alteration. In the Hadith: "Their clarity is like the clarity of the pearl that hands do not touch." Describing the beautiful women in such a way is common among the Arabs, from which is the saying:

She stood to reveal herself between the curtains of a canopy, like the sun on the day of its rising in the east, Or a pearl within a shell, whose diver is delighted, whenever he sees it, he rejoices and prostrates.

The prepositional phrase (the 'Ka' and the noun following it) is in the position of an adjective for al-Hur (the fair ones) or a state (hal). The use of the particle Ka (as/like) is for the sake of hyperbole in the comparison, and perhaps the matter is based on it, similar to saying "a hand like the moon."