Why did he think that Achav will kill him?
Rashi: This is like verse 12 explains - Ru'ach Hashem will take you away, and we will not find you. Malbim (11-12) - you have been hiding from him. Surely you merely seek to show him that he searched for elsewhere in vain, for you are here!
QUESTIONS ON RASHI
Rashi writes that Ru'ach Hashem will take Eliyahu away, and they will not find him, and Achav will kill Ovadyah. Why should he kill him? Ovadyah can say 'I saw Eliyahu, but realize that a wind is prone to take him!'
Kli Yakar: Achav will be insulted, as if I say, you searched everywhere for Eliyahu. Here he is - let us see your power, if you can overcome him! And even if I will be careful to say in a way that there is no insult, there is danger lest a wind take you
This is unlike Bamidbar Rabah 19:2, which says that Achav succeeded in war, even though his generation served idolatry, because they did not slander. Eliyahu said "I alone remain from Nevi'ei Hashem" (verse 22), and no one told the king that Ovadyah hid Nevi'ei Hashem! (PF)
Malbim: Achav did not kill him for this, for Izevel wanted to tell the Nevi'im, and not Achav.
