In The Name of Allaah, The Most Merciful, The Bestower of Mercy.

Allaah [The Most High] said:

إِنَّا مَكَّنَّا لَهُ فِي الْأَرْضِ وَآتَيْنَاهُ مِن كُلِّ شَيْءٍ سَبَبًا

فَأَتْبَعَ سَبَبًا

Verily, We established him (i.e. Dhul Qar’nayn) in the earth, and We gave him the means of everything. So he followed a way. [18:84-85]

Ali bin Abee Talhah reported from ibn Abbaas who said, ”[it is] knowledge.” Qataadah, Ibn Zaid, Ibn Jurayj and Dahhaak said, “[it is] knowledge which led him to what he wanted.” Ishaaq said, “[it is] knowledge that led him wherever he wanted to [reach or go].” Many of the Mufassiroon said that he [Dhul Qar’nayn] was given knowledge of everything that a person needs to aid himself.  So he followed a path through those means bestowed upon him to reach their [praiseworthy] goals. [Source:  An Excerpt from Badaa’i At-Tafseer Al-Jaami Limaa Fassarahu Al-Imaam Ibnul Qayyim Al-Jawziyyah..2/165]