I perceived that the portions of the Levites had not been given them: for the Levites … were fled. What Nehemiah saw was that the Levites were absent, and "the house of God forsaken" (verse 11). On inquiry, he found that the reason of their absence was the non-payment of the tithes.
That did the work. i.e. whose business it was to do the work of the house, or, in other words, conduct Divine service. Every one to his field. Every Levite had a plot of ground, which he cultivated when not engaged in the work of the temple (see Numbers 35:2; Joshua 21:3).