Of what do they assure him?
I hope I'm right, because your question isn't that specific. I'm going to assume that you are talking about the conspirators assuring Julius Caesar? After a particularly disturbing dream, Calpurnia, Caesar's wife, begs Caesar to stay home on the Ides of March. Caesar had originally planned to go to the Senate and address his "supports", but after hearing of Calpurnia's dream in which Caesar's blood is spewing from his statue, he decides to placate his wife and stay in. Shortly after, the conspirators arrive at his home and assure Caesar that he is perfectly safe; Calpurnia's dream has been misinterpreted, and the blood on the statue is actually a positive sign. Caesar soaks in the flattery and accompanies his killers to the Senate.