فَلْيَعْبُدُوا رَبَّ هَٰذَا الْبَيْتِ
So let them worship the Lord of this House. (106:3)
The fāʾ links the preceding favor to the ensuing response. Lām al-amr with the imperfect makes fal-yaʿbudū a command, not merely a statement about future behavior. A recollection of benefit becomes a demand for grateful action.
The prior verses explain the rhetorical force of the command: it is presented as the fitting consequence of the blessings recalled, not an unrelated new assertion.