Ester 8:10

10 Mordecai wrote in the name of King Xerxes, sealed the dispatches with the king's signet ring, and sent them by mounted couriers, who rode fast horses especially bred for the king.

10 The letters were sent in the name of King Ahasuerus and stamped with his ring, and they were taken by men on horseback, going on the quick-running horses used for the king's business, the offspring of his best horses: