The tribes of Reuben, Gad, and the half-tribe of Manasseh had settled on the east side of the Jordan River, separate from the other tribes of Israel. Concerned about future generations possibly being excluded from the community of Israel, they built an altar not for sacrifices, but as a symbol of their shared faith and commitment to God. This altar was meant to be a witness to their descendants and the other tribes that they too worship the Lord and have a rightful place among His people.
The verse underscores the importance of unity and continuity in faith, ensuring that geographical separations do not lead to spiritual divisions. It highlights the need for tangible reminders of faith that can be passed down through generations, reinforcing the idea that all tribes, regardless of their location, are part of the covenant community. This act of building an altar as a witness serves to prevent misunderstandings and conflicts, promoting peace and unity among the people of Israel.