Isaiah 37:34

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

Cross-reference

Isaiah 37:29 earlier in the same prophecy says God will turn the Assyrian back by the same way — verse 34 reiterates that promise.

Proverbs 21:30 states no wisdom or counsel can prevail against the Lord — explains why the Assyrian's plans to enter Jerusalem fail.