Al-Rahman and Al-Rahim are both derived from the root 'rahma' (mercy). Al-Rahman denotes a mercy that is vast, encompassing all of creation — believer and disbeliever alike receive sustenance, air, life, and existence through this universal mercy. Al-Rahim denotes a special, particular mercy reserved for the believers in the next world. The combination of both names after the name 'Allah' tells us that the Lord of all worlds governs His creation through two dimensions of mercy — one universal and one particular. This is why the Bismillah begins every Surah — every act undertaken in Allah's name is undertaken under the shelter of both His universal and particular mercy.

— Reflection, TathirQuran reflection — pending scholarly review