And he wrote in the king Ahasuerus' name, and sealed it with the king's ring, and sent letters by posts on horseback, and riders on mules, camels, and young dromedaries:

And he wrote the name of king Ahasuerus, and sealed it with the king's ring, and sent letters by post on horseback, riding on swift steeds that were used in the king's service, bred of the stud:

And these letters which were sent in the king's name, were sealed with his ring, and sent by posts: who were to run through all the provinces, to prevent the former letters with new messages.

And he wrote in the name of king Ahasuerus, and sealed it with the king's ring, and sent letters by couriers on horseback riding on coursers, horses of blood reared in the breeding studs:

And he wrote in the name of king Ahasuerus, and sealed it with the king's ring, and sent letters by posts on horseback, riding on swift steeds that were used in the king's service, bred of the stud:

And he wrote in the king Ahasuerus's name, and sealed it with the king's ring, and sent letters by posts on horseback, and riders on mules, camels, and young dromedaries:

And he writeth in the name of the king Ahasuerus, and sealeth with the signet of the king, and sendeth letters by the hand of the runners with horses, riders of the dromedary, the mules, the young mares,

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:

Riders on mules, camels and young dromedaries - Most moderns translate "riders upon coursers and mules, the offspring of mares;" but the words translated "mules" and "mares," are of very doubtful signification, since they scarcely occur elsewhere. The real meaning of the clause must remain doubtful; perhaps the true translation is, "riders upon coursers of the king's stud, offspring of high-bred steeds." So Esther 8:14.

On mules, camels, and young dromedaries - What these beasts were is difficult to say. The word רכש rechesh, which we translate mules, signifies a swift chariot horse.
The strange word אחשתרנים achashteranim is probably a Persian word, but perhaps incurably corrupted. The most likely derivation is that of Bochart, from the Persian akhash, huge, large, rough, and aster, a mule; large mules.
The words בני הרמכים beney harammachim, the sons of mares, which we translate dromedaries, are supposed to signify mules, produced between the he ass and the mare, to distinguish them from those produced between the stallion and the ass, But there is really so much confusion about these matters, and so little consent among learned men as to the signification of these words, and even the true knowledge of them is of such little importance, that we may well rest contented with such names as our modern translations have given us. They were, no doubt, the swiftest and hardiest beasts that the city or country could produce.

And he wrote in the King Ahasuerus' name, and sealed it with the king's ring,.... Which gave the letters authority, and made them irreversible, and for this Mordecai had the king's order, Esther 8:8
and sent letters by post; by runners or couriers:
on horseback; that rode on horses that were racers, that ran swiftly:
and riders on mules, camels, and young dromedaries; which were all different creatures, and swift ones, according to our version, especially the latter; see Jeremiah 2:23 which were a kind of camels, but swifter, and would go more than one hundred miles a day (a); and, as Diodorus Siculus says (b), not less than 1500 furlongs or about two hundred miles: though it may be only one sort are meant, namely, "mules", for the next word, "ahashteranim", in the Persian language signifies mules (c), and so Aben Ezra interprets it, and likewise Kimchi and Ben Melech; and the last words may be rendered "sons of mares", so David de Pomis; that is, such mules as are gendered by he asses and mares: and so the same writer observes, that the word in the Arabic language signifies "mares"; and such mules that come from them he says are stronger than those that come from she asses; so that the whole may be rendered to this sense, "riders on mules", (which in the Persian language are called "ahashteranim",) namely, such as are "sons of mares"; and which according to Aelianus (d) and Pliny (e) are the swiftest; though the Persians had camels swifter than are common elsewhere, called "revatrie", the "goer", which trot as fast as an horse can gallop (f).
(a) Isidor. Origin. l. 12. c. 1. Vid. Strabo Geograph. l. 15. p. 498. (b) Bibliothec. l. 19. p. 683. (c) Castell. Dictionar. Persic. col. 29. Hottinger. Smegma Oriental l. 1. c. 5. p. 75. (d) De Animal. l. 16. c. 9. (e) Nat. Hist. l. 8. c. 44. (f) Universal History, vol. 5. p. 88.

sent . . . by posts . . . and riders on . . . camels, and young dromedaries--The business being very urgent, the swiftest kind of camel would be employed, and so the word in the original denotes the wind-camel. Young dromedaries also are used to carry expresses, being remarkable for the nimbleness and ease of their movements. Animals of this description could convey the new rescript of Ahasuerus over the length and breadth of the Persian empire in time to relieve the unhappy Jews from the ban under which they lay.

Riders - Which were not employed in sending the former letter: but this coming later required more care and speed, that the Jews might be eased from their present fears, and have time to provide for their own defence.