Surah Yusuf — Ayah 104 (12:104)
وَمَا تَسۡـَٔلُهُمۡ عَلَيۡهِ مِنۡ أَجۡرٍۚ إِنۡ هُوَ إِلَّا ذِكۡرٞ لِّلۡعَٰلَمِينَ ١٠٤
English translation (Saheeh International)
And you do not ask of them for it any payment. It is not except a reminder to the worlds.
Brief commentary
If they used their reason they would believe the Messenger (peace be upon him), because he did not ask any reward for the Qur’ān or for what he called them to. The Qur’ān is only a reminder for all people.