5. not gone up into . . . gaps--metaphor from breaches made in a wall, to which the defenders ought to betake themselves in order to repel the entrance of the foe. The breach is that made in the theocracy through the nation's sin; and, unless it be made up, the vengeance of God will break in through it. Those who would advise the people to repentance are the restorers of the breach (Eze 22:30; Ps 106:23, 30).
      hedge--the law of God (Ps 80:12; Isa 5:2, 5); by violating it, the people stripped themselves of the fence of God's protection and lay exposed to the foe. The false prophets did not try to repair the evil by bringing back the people to the law with good counsels, or by checking the bad with reproofs. These two duties answer to the double office of defenders in case of a breach made in a wall: (1) To repair the breach from within; (2) To oppose the foe from without.
      to stand--that is, that the city may "stand."
      in . . . day of . . . Lord--In the day of the battle which God wages against Israel for their sins, ye do not try to stay God's vengeance by prayers, and by leading the nation to repentance.

JFB.