I have digged, and drunk water. Sennacherib notes three natural obstacles to his advance—the forces of his opponents he does not appear to account an obstacle—viz. mountains, deserts, rivers. Mountains do not stop him—he crosses them even with his chariot-force (Isaiah 37:24).
Deserts do not stop him—he digs wells there, and drinks their waters. Rivers will not stop him—he will dry them up, trample them into puddles. Note the contrast between the past tenses, "I have come up," "I have digged," "I have drunk," and the future, "I will dry up."
He had crossed the mountain ranges Sinjar, Amanus, Lebanon; he had passed waterless tracts, where he had had to dig wells, in Mesopotamia and Northern Syria. He was about to find his chief obstacle, rivers, when he invaded Lower Egypt.
The rivers of the besieged places; rather, the rivers of Egypt. Mazor, the singular form (compare Assyrian Muzr, and modern Arabic Misr), is used here (as in Micah 7:12, and perhaps in Isaiah 19:6), instead of the ordinary dual term, Mizraim, probably because Lower Egypt is especially intended.
Sennacherib was looking especially to the invasion of Lower Egypt,where the Nile had "seven branches" (Herod; Isaiah 2:17), and the country was also cut up by numerous canals, which would naturally constitute a great difficulty to a force depending mainly on its chariots.
He believed, however, in his heart, that he would find a way of "drying up" these "rivers."