21. there--namely, in Jerusalem.
      will be . . . rivers--Jehovah will be as a broad river surrounding our city (compare Isa 19:6; Na 3:8), and this, too, a river of such a kind as no ship of war can pass (compare Isa 26:1). Jerusalem had not the advantage of a river; Jehovah will be as one to it, affording all the advantages, without any of the disadvantages of one.
      galley with oars--war vessels of a long shape, and propelled by oars; merchant vessels were broader and carried sail.
      gallant--same Hebrew word as for "glorious," previously; "mighty" will suit both places; a ship of war is meant. No "mighty vessel" will dare to pass where the "mighty Lord" stands as our defense.

JFB.