Put/set somebody's mind at ease/rest - Idioms by The Free Dictionary
put/set somebody's mind at ease/rest
set someone's mind at ease (about someone or something)
to make someone feel mentally comfortable about someone or something. Alice is upset. I will have to do something to set her mind at ease about the accident. Please set your mind at ease. Everything will be all right.
put/set somebody’s ˈmind at ease/rest do or say something to somebody which stops them worrying about something: If you’d phoned me it would have put my mind at ease. ♢ He was nervous about meeting my parents, so I tried to set his mind at rest.