https://en.m.wikipedia.org/wiki/Frank_Pentangeli
"After the hearing, Corleone family consigliere Tom Hagen (Robert Duvall) visits Pentangeli in custody. Hagen tells Pentangeli, a history buff, a story about how traitors in ancient Rome could spare their families if they committed suicide; the implication being that Michael will take care of Pentangeli's family if he kills himself. Pentangeli thanks Hagen, returns to his assigned quarters, and slits his wrists while taking a bath."