The 99 Names · Names Most Often Paired in the Quran
Al-Waahid الواحد
The One, singular in every perfection, with no partner in any of it.
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. 169 ↗
The author explains this name together with: Al-Ahad
Evidence
﴿قُلۡ مَن رَّبُّ ٱلسَّمَٰوَٰتِ وَٱلۡأَرۡضِ قُلِ ٱللَّهُۚ قُلۡ أَفَٱتَّخَذۡتُم مِّن دُونِهِۦٓ أَوۡلِيَآءَ لَا يَمۡلِكُونَ لِأَنفُسِهِمۡ نَفۡعࣰا وَلَا ضَرࣰّاۚ قُلۡ هَلۡ يَسۡتَوِي ٱلۡأَعۡمَىٰ وَٱلۡبَصِيرُ أَمۡ هَلۡ تَسۡتَوِي ٱلظُّلُمَٰتُ وَٱلنُّورُۗ أَمۡ جَعَلُواْ لِلَّهِ شُرَكَآءَ خَلَقُواْ كَخَلۡقِهِۦ فَتَشَٰبَهَ ٱلۡخَلۡقُ عَلَيۡهِمۡۚ قُلِ ٱللَّهُ خَٰلِقُ كُلِّ شَيۡءࣲ وَهُوَ ٱلۡوَٰحِدُ ٱلۡقَهَّـٰرُ ١٦﴾
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 واحد، وحّد قلبي على طاعتك، ولا تجعل فيه تعلقًا بغيرك
O Allah, O Al-Waahid, unite my heart upon obeying You, and let it cling to none but You.
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).