John Gill Commentary Nehemiah 6

Now it came to pass, when Sanballat and Tobiah, and Geshem the Arabian, and the rest of our enemies, heard that I had builded the wall Quite finished it:

and that there was no breach left therein; but all was made up firm and strong:

though at that time I had not set up the doors upon the gates; not upon all of them, though some might by the particular builders of them; and they all of them might be ready made, though not as yet put upon the hinges.

Then Sanballat and Geshem sent unto me
Messengers:

saying, come, let us meet together in some one of the villages ;
in Cephirim, which Jarchi takes to be the name of a place, perhaps the same with Cephirah, a city in the tribe of Benjamin, (Joshua 18:26)

in the plain of Ono ;
which was in the same tribe, see (1 Chronicles 8:12) , they might pretend a friendly meeting, to accommodate differences between them, or to converse together about the general interest of the king of Persia in those parts:

but they thought to do me mischief ;
to kill him, or at least to confine him; this he either conjectured from their general character and behaviour, or he had intelligence of their design.

And I sent messengers unto them
He did not show any open contempt of them, nor did he even return answer by the messenger that came from them, but sent some of his own people to them:

saying, I am doing a great work ;
was about an affair of great importance, very busy, and not at leisure to give them a meeting:

so that I cannot come down ;
Jerusalem being built on an eminence, and the place proposed to meet at in a plain, going thither is expressed by coming down:

why should the work cease, while I leave it, and come down to you ?
signifying that it would cease if he left it; and it being of greater consequence than anything they could have to converse about, he argues it would be wrong to relinquish it on such an account; this was the reason he thought fit to give, but was not the only, nor the principal reason, which is suggested in the preceding verse.

Yet they sent unto me four times after this sort
Being very desirous of getting him into their hands, and therefore were very pressing and importunate:

and I answered them after the same manner ;
every time as before, he being as much bent on finishing the work as they were to divert him from it.

Then sent Sanballat his servant to me in like manner the
fifth time
In his own name, neither Tobiah nor Geshem joining with him, he being more solicitous and anxious to get him into his hands than any of them; and it may be, as some think, pretending more friendship for him than the rest, and therefore writes alone, as if they knew nothing of his writing:

with an open letter in his hand :
which having in it an intimation of Nehemiah being guilty of treason, anyone that would might read it, and so spread the defamation.