Imperative form does not always imply an enforceable order from a superior. When the speaker requests something from a higher authority, the force may be supplication (الدعاء). Among equals it may be entreaty (الالتماس). The form can also convey a wish for an unattainable or remote outcome.
«رَبِّ اغْفِرْ لِي»
My Lord, forgive me.
This is a prayer in the imperative form, not an assertion of superiority.
«أَلَا أَيُّهَا اللَّيْلُ الطَّوِيلُ أَلَا انْجَلِ»
O long night, would that you would pass away!
The speaker is voicing longing rather than treating the night as a subordinate who must obey. The relation of speaker to addressee and the possibility of the requested action determine the rhetorical classification.