וַיִּתְפַּלֵּ֤ל אֱלִישָׁע֙ וַיֹּאמַ֔ר יְהוָ֕ה פְּקַח־נָ֥א אֶת־עֵינָ֖יו וְיִרְאֶ֑ה וַיִּפְקַ֤ח יְהוָה֙ אֶת־עֵינֵ֣י הַנַּ֔עַר וַיַּ֗רְא וְהִנֵּ֨ה הָהָ֜ר מָלֵ֨א סוּסִ֥ים וְרֶ֛כֶב אֵ֖שׁ סְבִיבֹ֥ת אֱלִישָֽׁע׃
And Elisha prayed, and said: ‘LORD, I pray Thee, open his eyes, that he may see.’ And the LORD 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.
Read Kabbalistic (mystical) interpretations of II Kings 6:17: Zohar and classical Jewish mystical sources, free online.