«وَإِلَى رَبِّكَ فَارْغَبْ»
And turn your longing toward your Lord.
Ilā rabbika is a prepositional phrase related to the imperative farghab. Placing the directional phrase first highlights the proper object of desire. The context supports focusing that desire upon the Lord rather than alternative objects.
Not all fronting has the same effect. Here the imperative, the semantic direction of longing, and the surrounding address together support the rhetorical reading.