For there was a command from the king concerning the singers, an ordinance regulating their daily activities.
Having given an account of the principal persons that dwelt in Jerusalem (a larger account of whom he had before, Ch1 9:2, etc.), Nehemiah, in these verses, gives us some account of the other cities, in which dwelt the residue of Israel, Neh 11:20. It was requisite that Jerusalem should be replenished, yet not so as to drain the country.
Commenting on Nehemiah 11:20-36
THEIR NAMES. (Neh. 11:3-36) the chief of the province--that is, Judea. Nehemiah speaks of it, as it then was, a small appendix of the Persian empire. in the cities of Judah dwelt every one in his possession in their cities--The returned exiles, who had come from Babylon, repaired generally, and by a natural impulse, to the lands and cities throughout the country which had been anciently assigned them.
Commenting on Nehemiah 11:3-36
it was the king's commandment--It was the will of the Persian monarch in issuing his edict that the temple service should be revived in all its religious fulness and solemnity. As this special provision for the singers is said to have been by the king's commandment, the order was probably given at the request or suggestion of Ezra or Nehemiah.