Put/set somebody’s mind at ease/rest
Definition 1 of 1
Pro Tip 1/3Emotional Relief
Used when someone is relieved of stress or worry, often in a caring or supportive context. 
After hearing the test results were negative, that really set my mind at ease.
Pro Tip 2/3Calming Uncertainty
Ideal for situations where there is uncertainty or doubt, offering information or action to resolve it. 
Seeing the plane land safely put their minds at rest about flying.
Pro Tip 3/3Conversational Reassurance
Often used in everyday conversation when one person wants to reassure another. 
Don't worry, your car is fine — that should put your mind at ease.