[It's in his nature. But he considers the offer for a moment. Owe someone like him a favor? He's not sure that's a good idea. He's heroic, not stupid. Hmmm...]

Fine, but I get the chance to reject it if I think it's going to hurt people.

[And 'hurt' is broad intentionally. He's not going to do something for the other without consideration.]

But that works. You did something for me, I'll do something for you.

[He'd give Dabi one if he had an empty one, but he doesn't. He's not that good at aetheric engineering.]