Welcome, Juan! I think what you're remembering is that, after Hagen made his speech about the other families getting into the drug business if the Corleones didn't, the Don "seemed enormously impressed. Hagen was encouraged: "Maybe the Don would go for it." But then the Don rebuked him: "Do you have it in your notes that Sollozzo made his living before the war from prostitution? As the Tattaglias do now. Write that down before you forget it." The Don was rebuking Tom for not mentioning Sollozzo's having been in the prostitution business. That was a prejudice that the Don held--"he was notoriously straight-laced in matters of sex." That's when Tom knew that the Don would never go for Sollozzo's deal.