Shall compel thee to go a mile, go with him twain. - αγγαρευσει. This word is said to be derived from the Persians, among whom the king's messengers, or posts, were called Αγγαποι, or angari. This definition is given both by Hesychius and Suidas.
The Persian messengers had the royal authority for pressing horses, ships, and even men, to assist them in the business on which they were employed. These angari are now termed chappars, and serve to carry despatches between the court and the provinces. When a chappar sets out, the master of the horse furnishes him with a single horse; and, when that is weary, he dismounts the first man he meets, and takes his horse. There is no pardon for a traveler that refuses to let a chappar have his horse, nor for any other who should deny him the best horse in his stable. See Sir J. Chardin's and Hanway's Travels. For pressing post horses, etc., the Persian term is Sukhreh geriften. I find no Persian word exactly of the sound and signification of Αγγαρος; but the Arabic agharet signifies spurring a horse, attacking, plundering, etc. The Greek word itself is preserved among the rabbins in Hebrew characters, אנגריא angaria, and it has precisely the same meaning: viz. to be compelled by violence to do any particular service, especially of the public kind, by the king's authority. Lightfoot gives several instances of this in his Horae Talmudicae.
We are here exhorted to patience and forgiveness:
First, When we receive in our persons all sorts of insults and affronts, Matthew 5:39.
Secondly, When we are despoiled of our goods, Matthew 5:40.
Thirdly, When our bodies are forced to undergo all kinds of toils, vexations, and torments, Matthew 5:41.
The way to improve the injustice of man to our own advantage, is to exercise under it meekness, gentleness, and long-suffering, without which disposition of mind, no man can either be happy here or hereafter; for he that avenges himself must lose the mind of Christ, and thus suffer an injury ten thousand times greater than he can ever receive from man. Revenge, at such an expense, is dear indeed.

And whosoever shall compel thee to go a mile,.... The word rendered "compel", is generally said to be of Persic original; the "Angari", among the Persians, were the king's messengers, or those who rode post, and were maintained at the king's expenses; and had power to take horses, and other carriages, and even men, into their service, by force, when they had occasion for them: hence the word is used to force, or compel persons to do this or the other thing; the word is often to be met with in the Jewish writings, and is in them expounded to be (k), the taking of anything for the service of the king. David de Pomis renders it by "a yoke" (l); meaning, any servile work, which such, who were pressed into the king's service, were obliged unto. And (m) is used to compel persons to go along with others, to do any service; in which sense it is here used: and Christ advises, rather than to contend and quarrel with such a person, that obliges to go with him a mile, to
go with him twain: his meaning is, not to dispute such a matter, though it may be somewhat laborious and disagreeable, but comply, for the sake of peace. The Jews (n), in their blasphemous book of the birth of Christ, own that he gave advice in such words as these, when they introduce Peter thus speaking of him.
"He, that is, Jesus, hath warned and commanded you to do no more evil to a Jew; but if a Jew should say to a Nazarene, go with me one mile, he shall go with him two miles; and if a Jew shall smite him on the left cheek, he shall turn to him also the right.''
Can a Jew find fault with this advice?
(k) Vid. Maimon. & Bartenora in Misn. Bava Metzia, c. 6. sect. 3. (l) Tzemach David, fol. 8. 4. (m) Vid. Buxtorf. Lex. Rabb. p. 131, 132. (n) Toldos Jesu, p 22.

And whosoever shall compel thee to go a mile, go with him twain--an allusion, probably, to the practice of the Romans and some Eastern nations, who, when government despatches had to be forwarded, obliged the people not only to furnish horses and carriages, but to give personal attendance, often at great inconvenience, when required. But the thing here demanded is a readiness to submit to unreasonable demands of whatever kind, rather than raise quarrels, with all the evils resulting from them. What follows is a beautiful extension of this precept.

Compel thee to go a mile. In those days, when there were no stages, railroad trains, postal lines, or regular means of conveyance, it was common for officers traveling to impress men to assist them on the route. It was a necessary, but oppressive, exaction. Christ directs to yield the service, and double it rather than refuse it.
A mile. A Roman word from mille, a thousand. A Roman mile was a thousand paces, 1,520 yards.