Tafsir of Al-Kahf 18:85

His traveling and reaching the Place where the Sun sets (the West) Allah tells,

فٲتبع سببا

So he followed a way. Ibn Abbas said that; he followed different routes to achieve what he wanted. Mujahid said that; he followed different routes, east and west. According to one report narrated from Mujahid, he said:

سببا

(a way), means, "A route through the land.'' Qatadah said, "It means he followed the routes and landmarks of the earth.''