set one's mind at rest


Also, put one's mind at rest. Stop worrying, allay one's anxiety. For example, Your car's been found undamaged, so set your mind at rest. Also see lay at rest.

The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.