Behold, I will send a blast upon him. — Behold, I am about to put a spirit within him. “ ‘A spirit’ is probably not to be understood personally (comp. 1 Samuel 18:10; 1 Kings 22:21 seq.), but in the weaker sense of impulse, inclination. (Comp. Isaiah 19:14; Isaiah 29:10; Numbers 5:14; Hosea 4:12; Zechariah 13:2.) The two senses are, however, very closely connected” (Cheyne, on Isaiah 37:7). In fact, it may be doubted whether Hebrew thought was conscious of any distinction between them. The prophets believed that all acts and events — even the ruthless barbarities of Assyrian conquerors — were “Jehovah’s work.” The lowly wisdom of the peasant, as well as the art of good government, was a Divine inspiration (Isaiah 28:26; Isaiah 28:29; Isaiah 11:2).
And he shall hear... return. — To be closely connected with the preceding words. In consequence of the spirit of despondency or fear with which Jehovah will inspire him, he will hastily retire upon hearing ill news. The “rumour” or report intended is presently specified (2 Kings 19:9); “for though Sennacherib made one more attempt to bring about the surrender of Jerusalem, his courage must have left him when it failed, and the thought of retreat must have suggested itself, the execution of which was only accelerated by the blow which fell upon his army” (Keil and Thenius).