In the gospel of Luke Jesus had just given a very lengthy rebuke of the pharisees and lawyers. He was addressing their hypocrisy for essentially putting on a show and requiring all kinds of things from the common people while they themselves didn’t follow their own rules.
After a crowd pressed in on them to the point that people were being trampled, Jesus spoke to his disciples and said, “Beware of the leaven of the Pharisees, which is hypocrisy. Nothing is covered up that will not be revealed, or hidden that will not be known. Therefore whatever you have said in the dark shall be heard in the light, and what you have whispered in private rooms shall be proclaimed on the housetops” (Luke 12:1-3 ESV).
In other words, people will recognize hypocrisy. Whatever is happening in the dark reveals where your heart is. Unlike the Pharisees, Jesus is telling people to be the same wherever they are. He gives this message to his disciples because it was especially important for them to model consistent, moral behavior. There is a reckoning that is happening among religious leaders who privately are harsh and abusive but publicly look squeaky clean. Jesus was warning his disciples to remain holy at all times for the sake of the kingdom.