This sacred attribute is repeatedly used in the Holy Qur’an, invocations and in numerous narrations. This is considered by Gnostics and as the Great Name and is the Key to every hardship.
Rab, morphologically means the owner and the instructor. Allah is the possessor of all things and the instructor for the whole creation.
If a genuine servant of God considers these two senses of the word he will not have to be the servant of anybody except for Allah.
The true possessor of all creatures and the real instructor of every being is Allah.
source : The Book: Diar Aashiqan by prof, Hussain Ansarian