put someone's mind at rest
US /pʊt ˈsʌm.wʌnz maɪnd æt rɛst/
UK /pʊt ˈsʌm.wʌnz maɪnd æt rɛst/

1.
успокоить, развеять опасения
to tell someone something that makes them stop worrying
:
•
I called her to put her mind at rest about the children.
Я позвонил ей, чтобы успокоить ее насчет детей.
•
The doctor's explanation helped to put my mind at rest.
Объяснение доктора помогло успокоить меня.