Divine commandment over personal interest

قُلْ مَآ أَسْـَٔلُكُمْ عَلَيْهِ مِنْ أَجْرٍ وَمَآ أَنَا۠ مِنَ ٱلْمُتَكَلِّفِينَ

Say, [O Muḥammad], "I do not ask you for it [i.e., the Qur’ān] any payment, and I am not of the pretentious.