Esther seems to have been afraid to make her real request of Xerxes too abruptly. She concluded that the king would understand that she had a real petition in the background, and would recur to it, as in fact he did Esther 5:6; Esther 7:2.
Related Commentaries of Esther 5:4
Esther 5:4
4 And Esther answered, If it seem good unto the king, let the king and Haman come this day unto the banquet that I have prepared for him.