What contextual rhetorical effect does fī in la-fī khusr convey?

Supplementary Practice 19: Comparative Rhetorical Analysis of Sūrat al-ʿAṣr and al-Takāthur

• Negation of loss and affirmation of success
• A purely physical location with no bearing on condition
• Omission of the coming exception
• An image of being enveloped in the state of loss