When meeting Stilton in the hall in Chapter 14, what does Bertie say to stop Stilton from beating him up?

When Bertie goes out into the hallway in Chapter 14, he is expecting a beating from Stilton. To avoid this, Bertie reminds Stilton that they are partners for the Drone's Club darts competition and if Bertie gets hurt, it could cost Stilton money. Stilton realizes Bertie is right and lets him pass safely.