ElementReconstructed wordingExpressed wording
Head of annexationأَمْرُ — nominative subjectOmitted
Rabbرَبِّكَ — genitive complementرَبُّكَ — nominative subject
CauseGenitive annexationNew relation after deletion
A case label is meaningful only when the governing syntactic relation has been identified. Here the word “rabb” moves from genitive to nominative after the head “amr” has been omitted.
The deleted expression and the word with changed case are not necessarily the same item.