Charles Ellicott Commentary Nehemiah 10:28

"And the rest of the people, the priests, the Levites, the porters, the singers, the Nethinim, and all they that had separated themselves from the peoples of the lands unto the law of God, their wives, their sons, and their daughters, every one that had knowledge, and understanding;" — Nehemiah 10:28 (ASV)

All those who had separated themselves. —If these meant proselytes from heathenism, this verse would be a perfect description of the constituents of the people. But we have no record yet of a recognised body of such proselytes; and the word “separated” is the same as we find, with another meaning, in Nehemiah 9:2. Moreover, the following verses show that the covenant is particularly mindful of the danger to God’s law arising from interaction with the heathen.

Having understanding. —Children who could intelligently take the oath were included.