Book of Joel Chapter 2 Vs. 9

 The Day of the Lord

They shall run to and fro in the city; they shall run upon the wall, they shall climb up upon the houses; they shall enter in at the windows like a thief. Joel 2: 9

They shall run... Leap about from place to place, as locusts do (see Isa. 33:4).

they shall run... Which before they climbed; now they shall run upon, and go from tower to tower.

Joel had described their approach; they had come over “the tops of the mountains,” those which protected Jerusalem; and now he describes them scaling the walls, mounting the houses, entering the windows, running to and fro in the cities.

Here the description has reached its height. The city is given over to those who assault it. There remains nothing more, save the shaking of the heaven and the earth.

They shall climb up upon the houses, and enter in at the windows, like a thief; so the locusts entered into the houses of the Egyptians (Exo. 10:6); and Pliny says, they will eat through everything, and even the doors of houses.

Their houses were not airtight, and these locusts got into the houses, as well. There will be nothing safe before them.

Once more the relentless advance of God's army is emphasized (cf. Joel 2:4-5). They run like mighty men (supernatural beings), climb walls with no effort. They will stay the battle for God. Both advance in orderly fashion (Joel 2:7-8), plunge through defenses (Joel 2:8), and enter walled cities and homes.

As elsewhere in this section (cf. Joel 2:6), Joel seemingly alluded to Exo. 10:1-29.