Sura al-Isrāʾ 17:110

قُلِ ٱدْعُوا۟ ٱللَّـهَ أَوِ ٱدْعُوا۟ ٱلرَّحْمَٰنَ أَيًّا مَّا تَدْعُوا۟ فَلَهُ ٱلْأَسْمَآءُ ٱلْحُسْنَىٰ وَلَا تَجْهَرْ بِصَلَاتِكَ وَلَا تُخَافِتْ بِهَا وَٱبْتَغِ بَيْنَ ذَٰلِكَ سَبِيلًا

quli idʿū allāha awi idʿū l-raḥmāna ayyan mā tadʿū falahu l-asmāʾu l-ḥusnā wa-lā tajhar bi-ṣalātika wa-lā tukhāfit bihā wa-ibtaghi bayna dhālika sabīlan

Say: "Call upon Allah, or call upon Rahman: by whatever name ye call upon Him, (it is well): for to Him belong the Most Beautiful Names. Neither speak thy Prayer aloud, nor speak it in a low tone, but seek a middle course between."