דברי הימים א, פרק ה׳, פסוק ט׳

Economic growth and agricultural success often bring the unexpected challenge of needing more space. For this tribe, a massive increase in their flocks and cattle caused the land of Gilead to become too small to hold them. The pressing demand for new, wide pasture lands drove the people to move beyond their original borders and seek additional living spaces for their livestock.

Driven by these spatial and economic needs, a significant migration began toward the open areas of the east. This eastward settlement refers either to the entire tribe or to its leader [ביאור שטיינזלץ]. The primary approach among commentators is that they expanded into the regions east of Gilead. Even though their original territory was already located across the Jordan River in the eastern part of the Land of Israel, they continued to push further east.

Their expansion reached all the way to the desert and the Euphrates River, which traditionally marks the eastern border of the Land of Israel. Because the wilderness contained no geographical or political barriers, the tribe was able to spread freely. They continued moving outward into the desert until they reached the specific point where the Euphrates River comes closest to the Land of Israel [מצודת דוד, ביאור שטיינזלץ].