behold

The word "behold" here alerts us to pay attention to the surprising information that follows.

so they see all your nakedness

Stripping a person naked in front of others was an action intended to humiliate the person. The word "nakedness" can be translated as an adjective. Alternate translation: "so they can see you completely naked" (See: rc://en/ta/man/translate/figs-explicit and rc://en/ta/man/translate/figs-abstractnouns)