( formal ) used to emphasize that what you say is true or will definitely happen :
You may rest assured that we will do all we can to find him.
( formal ) used to emphasize that what you say is true or will definitely happen :
You may rest assured that we will do all we can to find him.
Oxford Advanced Learner's English Dictionary. Оксфордский английский словарь для изучающик язык на продвинутом уровне. 2005