Put your money where your mouth is
«Predicar con el ejemplo
When you put your money where your mouth is, you do what you have said you were going to. So, you are a person who is trust-worthy and whatever comes together with your words; your money, your reputation, etc. will be safe.
This expression has two possible origins: one from Ireland, where people use to mention this to those who are boasting about achieving fantastic feats so as to mean, «I want to see what you say becomes a reality.» The second possible origin is from poker. In this game, gamblers use to boast or show off about the hand they are having so as to confuse the opponents. So, if you have a good hand and you want to scare or warn your opponent to be careful with what they say, you tell them to put their money where their mouths are. A similar expression is «Put up or shut up!»
-OMG, I have put my foot in my mouth!
-What do you mean?
-Do you remember I told the principal that I could speak Japanese?
-Yes, but I know you, and I know you were just kidding.
-But the principal took it seriously and next week a board of Japanese educators is coming to visit the school, and the principal asked me to help with the translations.
-You see? You and your big mouth always get you into trouble! For that matter, I have always told you to put your money where your mouth is.