This verse can be separated into three clauses, with a main clause that the Lord will “change” the speech of the peoples into a “pure speech,” followed by two purpose clauses that detail the purpose for this change: “to call, all of them, upon the name of the Lord” and “to serve him with one accord.”
9 “For at that time I will change the speech of the peoples to a pure speech, that all of them may call upon the name of the LORD and serve him with one accord.