Surah Taha 20:59

قَالَ مَوْعِدُكُمْ يَوْمُ ٱلزِّينَةِ وَأَن يُحْشَرَ ٱلنَّاسُ ضُحًى

[Moses] said, "Your appointment is on the day of the festival when the people assemble at mid-morning."

Translation: Saheeh International

Tafsir

Said he Moses ‘Your tryst shall be the Day of Adornment — a festive day of theirs on which they adorn themselves and the public assemble — and let the people assemble let the inhabitants of Egypt gather at forenoon’ the time for this tryst to observe what will transpire.

Excerpt from Tafsir al-Jalalayn, commentary on 20:59, via Quran.com. The reader has the full commentary and 9 more tafsirs.