The Beneficent, the Merciful.
-Sura Al-Fatihah, Ayah 3
The meanings of Ar Rahman and Ar Raheem have been discussed in 1:1 here.
Tawhid Asma wa Sifat
The second dimension of Allah’s singularity is Tawhid asma wa sifat meaning Allah’s oneness in all His glorious names and attributes.
E.g. anyone can be strong but the strongest by far is none other than Allah.
Encouragement After Warning
In the previous ayah, Allah describes Himself as Lord of worlds, causing fear and awe for Him. This is neutralised by attributing Ar Rahman and Ar Raheem to Himself, which denote mercy and encouragement contrary to Allah and rabb which denote ownership and supremacy.
This is one of the esthetic values in Quran where Allah keeps His servants in balance and moderation by alternating between the extremes.
After the word Allah, Ar Rahman and Ar Rahim are of the most used words to refer to Allah in the Qur’an. This is to emphasise His mercy compared to His wrath. Despite being All Powerful and in control, His Mercy still preceeds His Wrath.
So have faith and never give up on Allah’s mercy.
Praise be to Allah.