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
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.