إِنَّا إِلَيْكُمْ مُرْسَلُونَ
Indeed, we have been sent to you.
رَبُّنَا يَعْلَمُ إِنَّا إِلَيْكُمْ لَمُرْسَلُونَ
Our Lord knows that we have surely been sent to you.
In Qur’an 36:14–16 the messengers’ claim meets increasing resistance. The latter wording brings more pronounced reinforcement: inna, the emphatic lām, and the appeal «رَبُّنَا يَعْلَمُ».
This illustrates how a speaker may intensify the statement in response to denial. The present lesson isolates that rhetorical movement, without attempting a full explanation of the entire narrative.