By the way that he came, by the same shall he return, and shall not come into this city, saith the LORD.

Jamieson-Fausset-Brown Bible Commentary

33. shall not come into this city-nor approach near enough to shoot an arrow, not even from the most powerful engine which throws missiles to the greatest distance, nor shall he occupy any part of the ground before the city by a fence, a mantelet, or covering for men employed in a siege, nor cast (raise) a bank (mound) of earth, overtopping the city walls, whence he may see and command the interior of the city. None of these, which were the principal modes of attack followed in ancient military art, should Sennacherib be permitted to adopt. Though the army under Rab-shakeh marched towards Jerusalem and encamped at a little distance with a view to blockade it, they delayed laying siege to it, probably waiting till the king, having taken Lachish and Libnah, should bring up his detachment, that with all the combined forces of Assyria they might invest the capital. So determined was this invader to conquer Judah and the neighboring countries (Isa 10:7), that nothing but a divine interposition could have saved Jerusalem. It might be supposed that the powerful monarch who overran Palestine and carried away the tribes of Israel, would leave memorials of his deeds on sculptured slabs, or votive bulls. A long and minute account of this expedition is contained in the Annals of Sennacherib, a translation of which has recently been made into English, and, in his remarks upon it, Colonel Rawlinson says the Assyrian version confirms the most important features of the Scripture account. The Jewish and Assyrian narratives of the campaign are, indeed, on the whole, strikingly illustrative of each other [Outlines of Assyrian History].

Matthew Henry's Concise Commentary

19:20-34 All Sennacherib's motions were under the Divine cognizance. God himself undertakes to defend the city; and that person, that place, cannot but be safe, which he undertakes to protect. The invasion of the Assyrians probably had prevented the land from being sown that year. The next is supposed to have been the sabbatical year, but the Lord engaged that the produce of the land should be sufficient for their support during those two years. As the performance of this promise was to be after the destruction of Sennacherib's army, it was a sign to Hezekiah's faith, assuring him of that present deliverance, as an earnest of the Lord's future care of the kingdom of Judah. This the Lord would perform, not for their righteousness, but his own glory. May our hearts be as good ground, that his word may strike root therein, and bring forth fruit in our lives.