God had put all of Jericho "under the ban" (Josh. 6:17 - NASB), meaning all the plunder belonged to him, not to individual soldiers. Against these specific instructions, Achan took spoils from Jericho (a robe, silver, and gold), resulting in Israel's defeat at Ai. By a process of elimination Achan was found out, and he and his children were stoned to death in the valley of Achor (Josh. 7). It is assumed that Achan's children were accomplices, as the law forbid children to be executed for their father's sin (Deut. 24:16).
