The answer is: Built an altar

Josh 22:10-12 - They thought the altar was built to worship other gods and so were ready to go to war until they realised it had been built as a witness to the true God.

In the Book of Joshua, we encounter a moment of tension and misunderstanding that illustrates how easily communication can break down, especially among communities with a shared history but different perspectives. When the tribes of Reuben, Gad, and the half-tribe of Manasseh built an altar near the Jordan, it triggered a wave of concern among their fellow Israelites. They perceived the altar as a potential betrayal, a step toward idolatry that could lead them away from their covenant with God.

What's fascinating here is how this situation unfolds. The leaders from the tribes west of the Jordan roused their warriors, ready to confront their brothers over what they interpreted as spiritual infidelity. At this moment, it’s significant to note the immediacy with which violence could have erupted. The stakes were high, as misunderstandings about worship can not only endanger community cohesion but also jeopardize a collective faith. Fortunately, communication saved the day when the eastern tribes clarified that their altar was not for sacrifices, but as a reminder—a “witness” to future generations of their shared commitment to God.

Additionally, we find a fascinating parallel in the New Testament. Paul often addressed similar concerns around division and misunderstanding among early Christian groups (like in Galatians). This narrative serves as a cautionary tale: such events remind us of the vital importance of discussion and understanding as opposed to jumping to conclusions—after all, unity and faith flourish best in the fertile ground of clear communication!