﴿ وَمَا تَسْـَٔلُهُمْ عَلَيْهِ مِنْ أَجْرٍ ۚ إِنْ هُوَ إِلَّا ذِكْرٌۭ لِّلْعَٰلَمِينَ ﴾

“although thou dost not ask of them any reward for it: it is but [God's] reminder unto all mankind.”

(Thou askest them) O Muhammad (no fee) no payment (for it) for the profession of monotheism. (It is) i.e. the Qur'an (naught else than a reminder) an admonition (unto the peoples) unto the jinn and humans.