Albert Barnes Commentary Esther 6:3

"And the king said, What honor and dignity hath been bestowed on Mordecai for this? Then said the king`s servants that ministered unto him, There is nothing done for him." — Esther 6:3 (ASV)

It was a settled principle of the Persian government that “Royal Benefactors” were to receive an adequate reward. The names of such persons were placed on a special roll, and care was taken that they should be properly recompensed, though they sometimes waited for months or years before they were rewarded.