Literal translation: The devil knows more because he’s old not because he’s the devil.
“Al perro mas flaco se le cargan mas las pulgas.”
Literal translation: The skinniest dog carries the most fleas.
Meaning – To pile on someone.
“Hasta lo que no se come le hacé daño”
Literal translation: Even what certain person does not eat makes that person ill. Referring to someone who is always upset about everything.