﴿ كَأَنَّهُنَّ بَيْضٌۭ مَّكْنُونٌۭ ﴾

“[as free of faults] as if they were hidden [ostrich] eggs.”

as if they were in terms of the starkness of their white colour hidden eggs of ostriches sheltered by their feathers from dust the colour being that whiteness with a hint of pallor which is the most beautiful of female complexions.