C. F. Keil and Franz Delitzsch on Numbers 24:19

Num 24:19

“And a ruler shall come out of Jacob, and destroy what is left out of cities.” The subject to ירדּ is indefinite, and to be supplied from the verb itself. We have to think of the ruler foretold as star and sceptre. The abbreviated form וירדּ is not used for the future ירדּה, but is jussive in its force. One out of Jacob shall rule. מעיר is employed in a collected and general sense, as in Psa 72:16. Out of every city in which there is a remnant of Edom, it shall be destroyed. שׁריד is equivalent to אדום שׁארית (Amo 9:12). The explanation, “destroy the remnant out of the city, namely, out of the holy city of Jerusalem” (Ewald and Baur), is forced, and cannot be sustained from the parallelism.