lay at rest
Also, lay to rest; set at rest. Satisfy, settle, as in I'll take care of it; you can set your mind at rest, or The arbitrator is sure to lay these questions to rest. [Late 1300s] Also see at rest; lay to rest.
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.