Albert Barnes Commentary 2 Kings 19:7

"Behold, I will put a spirit in him, and he shall hear tidings, and shall return to his own land; and I will cause him to fall by the sword in his own land." — 2 Kings 19:7 (ASV)

Will send a blast upon him — Rather, “I will put a spirit in him”—that is, “I will take from him his present pride and will put in him a new spirit, a spirit of craven fear.” Men will tell him of the destruction that has come upon his host (2 Kings 19:35), and he will immediately return, etc.