Joshua 1:12

And to the Reubenites, and to the Gadites, and to half the tribe of Manasseh, spake Joshua, saying,

Cross-references

Joshua 22:2 echoes the same charge—Joshua confirms the eastern tribes kept Moses' command, tying back to the original instruction.

Deuteronomy 3:18 records Moses' command to the Transjordan tribes to cross armed — the basis for Joshua's address here.