Joshua has given the land to the tribe of Reuben, Gad and the half tribe of Manasseh. They go possess the land and they build a altar for worshipping God but someone goes and tells Joshua that they have build a altar for worshipping but it not for God.  Sometimes we have people in our lives that see how good we are doing in our new place and they go and tell untruths to those that they hang around with , spreading rumors about what you are doing but they are not telling the truth about you.  Don't get mad at them, thank them for the free publicity.