put (one's) mind at ease
To reduce or remove one's worry, anxiety, dread, fear, etc. I know you're anxious to hear how your father is doing after the surgery, so let me put your mind at ease—he's going to make a full recovery. That bonus really put my mind at ease about these debts.
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.