بَلَغَنِي أَنَّ الطَّرِيقَ ضَاقَ بِالْمَارَّةِ. فَسِّحُوا الْمَمَرَّ.
I learned that the road is too narrow for passersby. So widen the passage.
The first sentence reports an issue and the next gives a directive. The initial fāʾ presents the command as a practical consequence of the report. It should not be treated as an unrestricted example of coordinating a declarative and an imperative with wāw; the actual connective has a different semantic role.
Replacing fāʾ with wāw could weaken the overt sense of consequence. A small change in a linking particle can reshape how the reader understands the relation between problem and remedy.