بِرَبِّ الْفَلَقِ
In the Lord of daybreak. (113:1)
Rabb is genitive after the preposition bi-, and al-falaq is its genitive complement. A well-established interpretation takes falaq to mean the breaking of dawn. Its placement before mention of threatening darkness gives the divine description contextual appropriateness.
This suitability is a rhetorical interpretation, not a grammatical consequence proving every later detail from the lexical form alone. Parsing and interpretive significance must be kept distinct.