William changed his name at sixteen to Rakim Allah
Cause Clarence 13X had New York on lock
Gods on every block

from Nas – U.B.R. (Unauthorized Biography of Rakim) Lyrics on Rap Genius

Meaning

Clarence 13X was a member of the Nation of Islam, and later started the Nation of Gods and Earths, also known as the 5 Percent Nation. The Nation has a great deal of influence on Hip Hop, especially those from New York (Nas himself studied from the 5 Percent Nation). Clarence 13X’s teachings inspired William Griffin so much that he took an Islamic name, Rakim Allah

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