Charles Ellicott Commentary Isaiah 37:7

"Behold, I will put a spirit in him, and he shall hear tidings, and shall return unto his own land; and I will cause him to fall by the sword in his own land." — Isaiah 37:7 (ASV)

I will send a blast upon him. — Better, I will put a spirit in him. The Authorised Version suggests the idea of some physical calamity, like that which actually destroyed the Assyrian army. Here, however, the “spirit” stands for the impulse, strong and mighty, which overpowers previous resolves .

He shall hear a rumour. — The words admit of being explained either as a prediction rising out of a purely supernatural foresight, or as resting on some secret intelligence which Israel had received as to the movements of Tirhakah.