Explanation:
You can configure a lock on a resource group to prevent the accidental deletion.
As an administrator, you may need to lock a subscription, resource group, or resource to prevent other users in your organization from accidentally deleting or modifying critical resources. You can set the lock level to CanNotDelete or ReadOnly. In the portal, the locks are called Delete and Read-only respectively.
* CanNotDelete means authorized users can still read and modify a resource, but they can't delete the resource.
* ReadOnly means authorized users can read a resource, but they can't delete or update the resource. Applying this lock is similar to restricting all authorized users to the permissions granted by the Reader role.
Reference:
https://docs.microsoft.com/en-us/azure/azure-resource-manager/resource-group-lock-resources