דברי הימים א, פרק י״ב, פסוק ל״ח

A massive force of fighters journeyed from the eastern side of the Jordan River, representing the tribes of Reuben, Gad, and the half-tribe of Manasseh. Numbering one hundred and twenty thousand men, they arrived in Hebron fully prepared for conflict. These warriors came equipped with every type of weapon and military gear required for an army heading into a major campaign [מצודת דוד, ביאור שטיינזלץ].

This overwhelming turnout served as a powerful expression of the nation's absolute unity and agreement. The mobilization was so sweeping that almost no one stayed behind. Acting with a single heart and overflowing with great joy, the entire nation gathered in Hebron for one shared purpose: to officially crown David as their king [רש״י].