I'm precise with it like Faheim with haircuts

from The Roots (Ft. Nelly Furtado) – Sacrifice Lyrics on Rap Genius

Meaning

Faheem is Black Thought’s barber (see quote and link, proof is at the end of the article).
Black Thought is saying here that he has enough experience under his belt to deliver the sharpest, most precise rhymes the same way Faheim gives him the best haircuts, which is why he’s been his barber for so long.

“His barber, Faheem Alexander, who grew up a few blocks from Trotter in Philadelphia, had been chiming in.”

http://www.capitalnewyork.com/article/culture/2011/12/4608911/dont-let-green-grass-fool-you-roots-are-one-most-respected-hip-hop-a?page=all

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