By the good hand of our God upon us. This is Ezra's usual mode of acknowledging the good providence and favour of Almighty God (see Ezra 7:6, Ezra 7:9, Ezra 7:27; and Ezra 8:31). Similar expressions occur also in Nehemiah (Nehemiah 2:8, Nehemiah 2:18), but not elsewhere in Scripture.
A man of understanding. In the Hebrew Ish-sekel, which some take for a proper name, but without any necessity. No such name is known to have existed; and the real name of "the man of understanding" appears to have been "Sherebiah," who is mentioned more than once in Nehemiah (Nehemiah 8:7; Nehemiah 9:4, Nehemiah 9:5) as a chief Levite.
And Sherebiah should be simply "Sherebiah." The preposition "and" (Hebrew ) ן has been inserted by a careless copyist.