When an organization is synchronizing their users and groups from an on-premises Active Directory, you need to perform membership changes in that on-premises directory. It is the source of authority, and changes made there synchronize into Azure Active Directory.
- Chapter 6 Manage Azure Security and Recovery Services
- from Exam Ref 70-533 Implementing Microsoft Azure Infrastructure Solutions
- Publisher: Microsoft Press
- Released: January 2018
The source of authority is the one that handles group membership access to an specific application.