﴿رَبِّ اشْرَحْ لِي صَدْرِي﴾
My Lord, expand my breast for me. (Ṭā Hā 20:25)
The request “ishraḥ lī” first introduces an act of expansion without yet identifying its object. The following “ṣadrī” specifies what is to be expanded. The listener's brief expectation is satisfied by the later constituent.
Grammatically, ishraḥ is an imperative, lī a prepositional phrase, and ṣadrī its object. Rhetorically, the crucial point is the momentary postponement of specification.