Reference: Surah Al-Kahf – Quran, Chapter 18, Verse 91: Arabic and English Translation
91. So (it was)! And We knew all about him (Dhul-Qarnain). (Translation by Muhsin Khan / Hilali)
Thus was the state of those people, and We encompassed in knowledge all concerning Dhu al- Qarnayn. (Translation by Abu Al-Alaa Maududi)
(He left them) as they were: We completely understood what was before him. (Translation by Yusuf Ali)


See Full Surah Al-Kahf