John Gill Commentary 2 Kings 8:13

"And Hazael said, But what is thy servant, who is but a dog, that he should do this great thing? And Elisha answered, Jehovah hath showed me that thou shalt be king over Syria." — 2 Kings 8:13 (ASV)

And Hazael said, but what, [is] your servant a dog, that he
should do this great thing ?
&c.] What do you take me to be, a vile, impudent, fierce, and cruel creature, as a dog, to be guilty of so great inhumanity and barbarity as this? or what is your servant? A dog, a mean abject creature, of no power and authority, incapable of doing such great things spoken of?

To which sense not only what is predicted of him, said to be great, inclines, but what follows:

and Elisha answered, the Lord has showed me that you shall be king
over Syria ;
and that you shall have power enough to do this; this declaration, according to Ben Gersom, was the anointing of him, predicted (1 Kings 19:15) .