Those shalt not take thee a wife - As it would be very inconvenient to have a family when the threatened desolations should come on the place. The reason is given in the following verses.
As marriage was obligatory upon the Jews, the prohibition of it to Jeremiah was a sign that the impending calamity was so great as to override all ordinary duties. Jeremiah was unmarried, but the force of the sign lay in its being an exception to the ordinary practice of the prophets.
In this place - The whole of Judaea.