As the LORD thy God liveth, there is no nation or kingdom, whither my lord hath not sent to seek thee: and when they said, He is not there; he took an oath of the kingdom and nation, that they found thee not. There is no nation or kingdom - He had sent through all his own states and to the neighboring governments to find out the prophet, as he knew, from his own declaration, that both rain and drought were to be the effect of his prayers. Had he found him, he no doubt intended to oblige him to procure rain, or punish him for having brought on this drought.
He took an oath - Ahab must have had considerable power and authority among the neighboring nations to require and exact this, and Elijah must have kept himself very secret to have shunned such an extensive and minute search.