According to the author of the book of Esther, this verse shows that Haman was able to get a special letter written and sent to many important people all over the land. He used the king's special ring to seal it, which meant it was very serious and official.
Esther 3:12: Then were the king's scribes called on the thirteenth day of the first month, and there was written according to all that Haman had commanded unto the king's lieutenants, and to the governors that [were] over every province, and to the rulers of every people of every province according to the writing thereof, and [to] every people after their language; in the name of king Ahasuerus was it written, and sealed with the king's ring. [scribes: or, secretaries]
This verse advises to "keep thee far from a false matter," which contradicts the decree in Esther 3:12 that was based on false accusations against the Jews.
Exodus 23:7: Keep thee far from a false matter; and the innocent and righteous slay thou not: for I will not justify the wicked.