I ain't no joke, I used to let the mic smoke
A common theme used for rap puns, metaphors, smiles, etc. is fire and smoke.
Often fire is attributed to one having great lines and verses, therefore in this line, Rakim declares that he would let microphones with which he rapped smoke, as a result of him spitting fire a.k.a. spitting great rhymes and verses.
Pictured above: How Rakim leaves the mic after he’s done rapping
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