Surah Al-Kahf 18:91

كَذَٰلِكَ وَقَدْ أَحَطْنَا بِمَا لَدَيْهِ خُبْرًا

Thus. And We had encompassed [all] that he had in knowledge.

Translation: Saheeh International

Tafsir

So it was in other words the situation was as We have stated; and We encompassed whatever pertained to him that is what Dhū’l-Qarnayn possessed in the way of machinery men and otherwise in knowledge.

Excerpt from Tafsir al-Jalalayn, commentary on 18:91, via Quran.com. The reader has the full commentary and 9 more tafsirs.