ישעיהו, פרק ל״ז, פסוק ח׳

Following the campaign at Jerusalem, a shift in the Assyrian military positions takes place. Rabshakeh withdraws from the city, intending to return to his base and report back to his master, Sennacherib, the King of Assyria. However, upon his retreat, he discovers that the army is no longer where he left them. He receives word that the king has abandoned the siege he was previously conducting on the city of Lachish. This prompts Rabshakeh to set out on a journey, searching wherever necessary to locate his master [מצודת דוד].

Eventually, Rabshakeh tracks down Sennacherib and finds him actively waging war against the important city of Libnah, which is situated in the same general region as Lachish [ביאור שטיינזלץ]. It is assumed that the king's decision to abandon the siege of Lachish and move his forces to Libnah was driven by practical military strategy. He calculated that it would be easier and more convenient to conquer Libnah rather than continuing the fight for Lachish [שד״ל].