Surah Al-Waqi'ah 56:78

فِى كِتَـٰبٍ مَّكْنُونٍ

In a Register well-protected;.

Translation: Saheeh International

Tafsir

in a Book inscribed guarded preserved and this is the Mushaf;

Excerpt from Tafsir al-Jalalayn, commentary on 56:78, via Quran.com. The reader has the full commentary and 9 more tafsirs.