Final answer:
Sonny's mother advised the boys to obey their father and stay out of his way.
Step-by-step explanation:
In the story, Sonny's mother advised the boys not to argue with their father and to obey him. She told them to stay out of their father's way and not to interfere with his plans. She also reminded them that their father had worked hard and knew what he was doing. By following their father's instructions and showing him respect, they would be able to avoid any conflicts.