Nah, Brah
You say it when someone is asking for something but they forgot to give you what they owed you. You’re basically saying, 'I’m not falling for this again.'
Nah, Brah, you didn’t bring me snacks last time. You’re not getting my help today.
Nah, Brah, I’m not doing your homework again. You owe me a pizza.
Nah, Brah, I said I’d help you cheat, not cover for your dumbass.