The African and Arab go at it they most Muslim

from Nas (Ft. Damian Marley & K'naan) – Tribes At War Lyrics on Rap Genius

Meaning

It is a reference to a double identity considering that Arabs in North Africa ie Egypt, Sudan, Algeria can be considered African as well as Arab by their adaption of the Arabic language and identity. Both peoples are all Muslims and equally Africans no matter if they speak Arabic or another African language.

And since they are all Muslims/Brothers why are they fighting and enslaving each other?

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