Jeremiah
1 Kings 18:10ESV·traditional attribution

As the LORD your God lives, there is no nation or kingdom where my lord has not sent to seek you. And when they would say, ‘He is not here,’ he would take an oath of the kingdom or nation, that they had not found you.

Matthew Henry Presbyterian @wholebiblehenry

In these verses we find, I. The sad state of Israel at this time, upon two accounts: - 1. Jezebel cut off the prophets of the Lord (Kg1 18:4), slew them, Kg1 18:13. Being an idolater, she was a persecutor, and made Ahab one.

Commenting on 1 Kings 18:1-16

John Gill Reformed Baptist @doctorgill

As the Lord thy God liveth,.... Which is the form of an oath he thought fit to make, to ascertain the truth of what he was about to say: there is no nation or kingdom, whither my lord hath not sent to seek thee; which is either an hyperbolical expression, signifying he had sought for him in many places, and in every place he could...

Adam Clarke Methodist @methodicalclarke

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.