On Sean Hannity's show last night, he advised people in Trump's orbit not to cooperate with Special Counsel Robert Mueller III. He doesn't want people to trust the FBI or listen to law enforcement.
Hannity, who is a huge supporter of the president, wants people to know that talking with the special counsel's office might lead to perjury charges. Any slip-up or poorly worded statement could come back to haunt them in the form of an indictment. The special prosecutor likely doesn't ask questions they don't know the answers. All of the people who pleaded guilty to lying to Mueller's office admitted to lying. Meaning, they knew what they told investigators was not true. It wasn't a misunderstanding, rather a willful attempt to cover up the truth.
People who have pleaded guilty like Micheal Cohen, Michael Flynn have cooperated with Mueller to receive a shorters sentence or probation. It appears Hannity is worried that the more people talk, the more the president gets implicated in a crime.
Mueller's office is looking into Russian cooperation with the Trump campaign & whether Trump obstructed justice.