John Gill Commentary Nehemiah 4:1

"But it came to pass that, when Sanballat heard that we were building the wall, he was wroth, and took great indignation, and mocked the Jews." — Nehemiah 4:1 (ASV)

But it came to pass, that when Sanballat heard that we
builded the wall
Or were building it; for as yet it was not finished, see (Nehemiah 4:6) ,

he was wroth, and took great indignation ;
inwardly, though outwardly he pretended to treat the work with contempt, as if it never would be accomplished, which yet he feared:

and mocked the Jews ;
as a set of foolish builders, and unable to finish what they had begun.