Please the exact reference in scripture or even Islamic history to back up this idea being “islamic”.
Early Muslim expansion was often organized around local leaders, tribal affiliations, and regional rulers united under larger caliphates but not necessarily bound by a religious command to have defined borders. Tribal loyalties and local political power shaped early Muslim territories, with different Muslim groups existing semi-independently under shared Islamic leadership. There was no strict religious rule forcing Muslim states to have exact borders or control over specific lands.
When it comes to travel between Muslim states, the Quran encourages migration mainly for religious freedom or safety, but it does not demand unrestricted travel between Muslim lands.
Historically, allowing free movement depended on political and social circumstances rather than religious scripture alone. So, the idea that Muslims from one state should always be able to travel freely to another is not a strict rule from early Islamic texts but depends on practical governance and local agreements.