The 99 Names · The Closing Verses of Surat Al-Hashr
Al-Mu'min المؤمن
The One who praised Himself with attributes of perfection, and affirmed the truth of His messengers with signs and proofs.
Explanation
A detailed explanation of this name (in Arabic) is in: Sharh Asma' Allah al-Husna fi Daw' al-Kitab wa al-Sunnah — Dr. Sa'eed ibn 'Ali ibn Wahf al-Qahtani — p. 172 ↗
Evidence
﴿هُوَ ٱللَّهُ ٱلَّذِي لَآ إِلَٰهَ إِلَّا هُوَ ٱلۡمَلِكُ ٱلۡقُدُّوسُ ٱلسَّلَٰمُ ٱلۡمُؤۡمِنُ ٱلۡمُهَيۡمِنُ ٱلۡعَزِيزُ ٱلۡجَبَّارُ ٱلۡمُتَكَبِّرُۚ سُبۡحَٰنَ ٱللَّهِ عَمَّا يُشۡرِكُونَ ٢٣﴾
Call upon Allah by this name
“To Allah belong the Beautiful Names, so call upon Him by them” — Al-A'raf 180
Example for practice
اللهم يا مؤمن، آمِن روعاتي، واجعلني من المؤمنين الآمنين يوم الفزع الأكبر
O Allah, O Al-Mu'min, calm my fears, and make me among the believers who are safe on the Day of the Greatest Terror.
An example for practice, not a transmitted text — following the Quranic way of closing a request with the fitting name (see Ibn al-Qayyim, Bada'i' al-Fawa'id 2/249).