Tafsir of Ghafir 40:19

"The treachery" (al-khā’inah): An adjective describing the glance, or a verbal noun (maṣdar) meaning "betrayal," similar to al-ʿāfiyah (well-being) meaning al-muʿāfāh (being granted health).

The intended meaning is: stealing a glance at what is not permissible, as those who harbor suspicion do. It is not appropriate to interpret "the treachery" as belonging to the eyes themselves, because the subsequent phrase, "and what the breasts conceal," would not be parallel to it.

If you ask: To what does the statement "He knows the treachery of the eyes" connect?

I say: It is one of the predicates of "He" in the verse, "He is the One who shows you..." (Ghafir: 12), similar to "He casts the Spirit..." (Ghafir: 15). However, "He casts the Spirit" was followed by the explanation, "to warn of the Day of Meeting" (Ghafir: 15), and then the discourse digressed to mention the conditions of the Day of Meeting up to the verse, "and no intercessor who is obeyed" (Ghafir: 18). Thus, it became distant from its counterparts.

"And Allah judges with the truth, while those they invoke besides Him do not judge with anything. Indeed, Allah is the Hearing, the Seeing."