Whether a sentence acts as a report or an expressive utterance is decided by its discourse setting, speaker intention and the addressee’s expectations—not by verb tense alone. “Raḥimahu Allāh” may be a prayer, while a comparable past-tense clause in historical narrative may truly be a report.
A reliable translation procedure is to identify the literal form, examine its context, and render the intended force. This applies equally to vocatives of wonder and declaratives used as requests.