This phrase is used when someone says something that happens right after or very soon. It's similar to the English expression 'Speak of the devil' but it's not used with a negative connotation. Instead, it's used to express surprise when something that was just mentioned happens or becomes true.
Examples
- Spanish: Hablaste de las vacaciones de verano y justo ahora mi jefe me da dos semanas libres. ¡Hablaste por boca de santo!
- English: You talked about summer holidays and just now my boss gave me two weeks off. You spoke through a saint's mouth!