John Gill Commentary 2 Kings 6:17

"And Elisha prayed, and said, Jehovah, I pray thee, open his eyes, that he may see. And Jehovah opened the eyes of the young man; and he saw: and, behold, the mountain was full of horses and chariots of fire round about Elisha." — 2 Kings 6:17 (ASV)

And Elisha prayed, and said, Lord, I pray you, open his eyes,
that he may see
Not the eyes of his body, which were not shut nor blinded, but the eyes of his mind; or, in other words, grant him a vision, represented in so strong a light, as to remove his fears:

and the Lord opened the eyes of the young man, and he saw ;
he had a vision of angels:

and, behold, the mountain ;
on which the city was built, or one near it:

was full of horses and chariots of fire ;
angels in this form, as in (2 Kings 2:11) , and these were

round about Elisha ;
being round about the city where he was; or rather so in the vision it was represented to the young man, he saw his master surrounded with horses and chariots of fire, in the utmost safety.