Surat Al A`raf: (180-181)

{وَلِلّهِ الأَسْمَاء الْحُسْنَى فَادْعُوهُ بِهَا وَذَرُواْ الَّذِينَ يُلْحِدُونَ فِي أَسْمَآئِهِ سَيُجْزَوْنَ مَا كَانُواْ يَعْمَلُونَ} [الأعراف: 180]

180- And to Allah belong the most beautiful names because they indicate the best and most honorable meanings, so invoke Allah by these venerable names. Moreover, leave aside those who deviate from the truth to falsehood as polytheists did when they called names to their alleged gods. They distorted the name of Allah to "Al Lat" and the name of "Al `Aziz" to "Al `Uzza". Those who distorted the names of Allah and deviated from the course for which they were revealed shall receive the punishment exactly as those who denied or distorted their meanings.

Allah's Names are bound by the Shari`ah, so it is not permissible for a person to make them up or invent them from his own; so it is not permissible for example to name Allah with "reasonable" or "well-understanding" but He must be called or invoked by His Names that are mentioned in the Qur'an and authentic Sunnah.

{وَمِمَّنْ خَلَقْنَا أُمَّةٌ يَهْدُونَ بِالْحَقِّ وَبِهِ يَعْدِلُونَ} [الأعراف: 181]

181- Of the nations which We created is a virtuous nation who are guided, guide the people to the truth, and act according to it in their worldly and hereafter affairs with others and with their own; those people exist in every time and place.