33 Heb “Raise a banner against the walls of Babylon.”
34 Heb “Strengthen the watch.”
35 Heb “Station the guards.”
36 Heb “Prepare ambushes.” The commands are here addressed to the kings of the Medes to fully blockade the city by posting watchmen and setting men in ambush to prevent people from escaping from the city (cf. 2 Kgs 25:4).
37 Heb “For the Lord has both planned and done what he said concerning the people living in Babylon,” i.e., “he has carried out what he planned.” Here is an obvious case where the perfects are to be interpreted as prophetic; the commands imply that the attack is still future.

In other versions

“Set up a standard against the walls of Babylon;

make the watch strong;

set up watchmen;

prepare the ambushes;

for the Lord has both planned and done

what he spoke concerning the inhabitants of Babylon.

Lift up a banner against the walls of Babylon!

Reinforce the guard,

station the watchmen,

prepare an ambush!

The Lord will carry out his purpose,

his decree against the people of Babylon.

Raise up a signal flag

against the walls of Babylon;

fortify the watch post;

set the watchmen in place;

prepare the ambush.

For the Lord has both planned and accomplished

what he has threatened

against those who live in Babylon.

Raise the battle flag against Babylon!

Reinforce the guard and station the watchmen.

Prepare an ambush,

for the Lord will fulfill all his plans against Babylon.

Against the walls of Babylon raise a banner;

post a strong watch, post watchmen, prepare the ambushes,

for Yahweh has both planned as well as performed

what he has spoken concerning the inhabitants of Babylon.

Set up the standard upon the walls of Babylon,

Make the watch strong, set up the watchmen,

Prepare the ambushes:

For the Lord hath both devised and done

That which he spake against the inhabitants of Babylon.

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