Following are a number of back-translations as well as a sample translation for translators of Joshua 6:26:

• Kupsabiny: “Then Joshua said, ‘Cursed by God be any person/man who builds again the city of Jericho. (His) firstborn son shall die when he begins to build the wall of the city, and when the building of the wall is about to be finished, all his sons have died.’” (Source: Kupsabiny Back Translation)
• Newari: “At that time Joshua pronounced this solemn oath,
  "If anyone tries to rebuild the city of Jericho,
  May a curse of the LORD fall upon him.
  May the firstborn son of the man who lays its foundations die,
  May the youngest son of the man who builds it gates die."” (Source: Newari Back Translation)
• Hiligaynon: “At that time, Josue warned the Israelinhon: ‘Cursed by the LORD (is) anyone who would-try again to-build/[lit. cause-to-stand] this city of Jerico. The one-who-builds its foundation will-lose/[lit. will-experience-the-death] (his) oldest son. The one-who-builds its gates/[lit. doors] will-lose/[will-experience-the-death] (his) youngest son.’” (Source: Hiligaynon Back Translation)
• English: “At that time, Joshua warned the people, ‘Yahweh will curse/punish anyone who tries to rebuild this city, Jericho. When that person lays/builds its foundation, his oldest son will die. And when he finishes building the city wall and sets up its gates, his youngest son will die.’” (Source: Translation for Translators)