The source says a fronted non-subject expression can be governed by what follows the fāʾ. In this example, yawma depends on munṭaliqun as a time adverbial.
Opening interactive controls...
Source: The Governor of the Adverbial
Conditional Particles: In, Law and Ammā
The source says a fronted non-subject expression can be governed by what follows the fāʾ. In this example, yawma depends on munṭaliqun as a time adverbial.