Rabb Rabb has three meanings: (i) Lord and Master; (ii) Sustainer, Provider, Supporter, Nourisher and Guardian, and (iii) Sovereign and Ruler, He who controls and directs. God is Rabb in all the three meanings of the term. The rational of the basic Qur`anic message - `serve none but God` - is that since God is man`s Rabb - Lord, Sustainer, Provider, Nourisher, etc. He alone should be the object of man`s worship and service. See, for example, Qur`an 2:21.