فَسَبِّحْ بِحَمْدِ رَبِّكَ
Then glorify your Lord with praise. (110:3)
The initial fāʾ responds to the earlier idhā frame and is commonly described as fāʾ of the response. Sabbiḥ is an imperative. The point of announcing help and victory is not merely celebration, but a directive toward glorification and praise.
Ignoring the fāʾ obscures the purposeful link between the described circumstance and the required action. The transition from report to command fits the situation.