I will send a blast "I will infuse a spirit into him" - "רוח בו נותין nothen bo roach never signifies any thing but putting a spirit into a person: this was πνευμα δειλιας, the spirit of deceit." - Secker. "I will send a blast" - I do not think that Archbishop Secker has hit the true meaning of these words. I believe רוח ruach means here a pestilential wind, such as the Arabs call simoom, that instantly suffocates both man and beast; and is what is termed "the angel of the Lord," God's messenger of death to the Assyrians, Isaiah 37:36.
Behold, I will send a blast upon him - Margin, ‹Put a spirit into him.‘ The word rendered ‹blast‘ (רוח rûach ) is commonly rendered ‹spirit.‘ It may denote breath, air, soul, or spirit. There is no reason to think that the word is used here in the sense of blast of wind, as our translators seem to have supposed. The sense is probably, ‹I will infuse into him a spirit of fear, by which be shall be alarmed by the rumour which he shall hear, and return to his own land.‘ The word is often used in this sense (compare 1 Samuel 16:14; see also Isaiah 31:8-9). Gesenius understands it here in the sense of will or disposition. ‹I will change his will or disposition, so that he will return to his own land.‘
And he shall hear a rumour - The rumour or report here referred to, was doubtless that respecting Tirhakah king of Ethiopia Isaiah 37:9. It was this which would alarm him, and drive him in haste from the cities which he was now besieging, and be the means of expelling him from the land.
And I will cause him - This is said in accordance with the usual statements in the Scriptures, that all events are under God‘s providential control (compare the note at Isaiah 10:5-6).
By the sword in his own land - (See the note at Isaiah 37:38).