John Gill Commentary 1 Kings 18:12

"And it will come to pass, as soon as I am gone from thee, that the Spirit of Jehovah will carry thee whither I know not; and so when I come and tell Ahab, and he cannot find thee, he will slay me: but I thy servant fear Jehovah from my youth." — 1 Kings 18:12 (ASV)

And it shall come to pass, as soon as I am gone from you,
that the Spirit of the Lord shall carry you where I do not know
This he supposed might possibly, and very probably, be the case, since small raptures might have been already, and known to Obadiah, as there were afterwards, see (2 Kings 2:16) (Ezekiel 3:12Ezekiel 3:14) (Acts 8:39), and then he should not know where he was, nor be able to direct his master where to find him:

and so when I come and tell Ahab, and he cannot find you, he shall
slay me ;
for telling him a lie, and deceiving and mocking him; or for not seizing on Elijah, and bringing him, when he knew he was so desirous of getting him into his hands:

but I your servant fear the Lord from my youth ;
and therefore did not deserve to be treated after this manner, having been an early and conscientious worshipper of the true God.