From Longman Dictionary of Contemporary Englishset/put somebody’s mind at restset/put somebody’s mind at rest (also set/put somebody’s mind at ease)WORRIED to make someone feel less worried or anxious If you’re worried, see a doctor to set your mind at rest. → mind
Examples from the Corpus
set/put somebody’s mind at rest• Just to put your mind at ease, we will get a second opinion from a cardiac specialist.• But she'd like to see him, to try and set her mind at rest.• I wish I could put their minds at rest.• The doctor set my mind at rest by explaining exactly what effect the drug would have on me.• It puts my mind at rest.• But let me set your mind at rest.• He must set their minds at rest about the Freddie affair, because they knew of Freddie.• He's been very kind to me and Lily, as regards putting our minds at rest about Stella.• He's unlikely to know how you feel, and until he does, he can't put your mind at rest.• Quite often, all that is required is a friendly chat to put your mind at rest. 