Isaiah 21:9

And, behold ... a chariot of men -This place shows that the word ‘chariot’ (רכבrekeb) may denote something else than a wagon or carriage, as a chariot drawn by men cannot be intended. The sense can be expressed, perhaps, by the word “riding,” ‘I see a riding of men approach;’ that is, I see “cavalry” drawing near, or men riding and hastening to the battle. With a couple of horsemen -The word ‘with’ is not in the Hebrew. The meaning is, ‘I see a riding of men, or cavalry; and they come in pairs, or two abreast.’ A part of the sentence is to be supplied fromIsaiah 21:7. He saw not only horsemen, but riders on donkeys and camels. And he answered -That is, the watchman answered.