Matthew Poole and continuators on Esther 2:19

19 And when the virgins were gathered together the second time , then Mordecai sat in the kings gate .

Either 1. When Esther with others were brought to the Kings house as it was decreed above. v. 2, 3. which is called the second time, because they had taken this course once before when Vashti was chosen Queen; But there is no mention of any such former use; and by the manner of proposing, it seems to have been a new project. Or, 2. Since Esther was declared Queen; for though that point was determined, the the Kings lust was not yet satisfied, and therefore being pleased with the for mer experiment, he desired another collection of Virgins whom he might make his Concubines. And this seems best to agree with the following words. For it is not probable that Mordecai sate at the kings gate till Esther was Queen: for till then he only walked before the court of the womens house, as is expressed. v. 11.

Either 1. Voluntarily, to learn the pregress of afairs. Or, rather 2. By office, as one of the Kings guard or Ministers: being advanced to this place by Esthers favour, though without any discovery of her relation to him.