The 3 sieves? " "Yes," said Socrates. Before I tell all sorts of things on others, it is worth taking the time to filter what we would say. This is what I call the 3 test sieves.
Sure. I just heard ... " "Very well. You do not know if it's true.
So," continued Socrates, will you tell me bad things about him and you're not even sure if they are true.
Moral of the story
When we have not something useful to say, it is better to remain silent.
Or "when there is doubt it is better to refrain".