Surah Al-Buruj 85:3

وَشَاهِدٍ وَمَشْهُودٍ

And [by] the witness and what is witnessed,

Translation: Saheeh International

Tafsir

and by the witness Friday and the witnessed the day of ‘Arafa — that is how these three elements have been explained in hadīth for the first one is ‘promised’ the second one is ‘a witness’ that testifies to deeds performed in it while the third is ‘witnessed’ by mankind and angels the introductory particle of the …

Excerpt from Tafsir al-Jalalayn, commentary on 85:3, via Quran.com. The reader has the full commentary and 9 more tafsirs.