“Ar-Rahman and Ar-Rahim are both derived from Rahmat, signifying tenderness requiring the exercise of beneficience (Raghib Imam) and thus comprising the idea of love and mercy. Ar-Rahman and Ar-Rahim are both active participle nouns of different measures. denoting intensiveness of significance, the former being of the measure fa’lan, and indicating the greatest preponderance of the quality of mercy, and the latter being of the measure fa’il and being expressive of a constant repetition and manifestation of the attribute. (A. H.) The two words have been explained by the holy prophet himself. He is reported to have said.
‘Ar-Rahman is the Beneficent God whose love and mercy are manifested in the creation of this world, and Ar-Rahim is the Merciful God whose love and mercy are manifested in the state that comes after’. (A . H.) i.e., in the consequence of the deeds of men.
Thus the attribute of mercy in Ar-Rahman is manifested before man comes in existence in the creation of things that are necessary for his life here, and therefore without his having deserved them, while the same attribute in Ar-Rahim is manifested when man has done something to deserve it. Thus the former is expressive of the utmost degree of the love and generosity, the latter of unbounded and constant favour and mercy. Lexicologists agree in holding that the former includes both the believer and the unbeliever for its object, while the latter particularises more the believer. (LL. R. gh. L.A. T.A.)
Hence I render Ar-Rahman as meaning the Beneficient God because the idea of doing good is predominent in it, though I must admit that the English language lacks an equivalent of Ar-Rahman even making an approach to giving expression to all comprehensive love and goodness manifested in that word……” (Mohammed Ali’s translation of the Koran, Foot Note 3.)
“Compassionate” is the translation of the Arabic word “Raoof” which according to Bokari (Vol. 2. P. 299) means “very great mercy.” Raoof “denotes a more special and a more tender affection than Rahmet, or the utmost degree thereof.”(Arabic English Lexicon by Lane.)