My momma believed in me, she let me use her van to go to the studio
Even though she know her tank is empty, that's who I do it fo'

from Kendrick Lamar – Wanna Be Heard Lyrics on Rap Genius

Meaning

His mom supported his dream and sacrificed for him to accomplish it, which is who he is doing it for. So she can live a more comfortable life when he becomes successful, he’ll look after her.

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