Surah Ya-Sin 36:39

وَٱلْقَمَرَ قَدَّرْنَـٰهُ مَنَازِلَ حَتَّىٰ عَادَ كَٱلْعُرْجُونِ ٱلْقَدِيمِ

And the moon - We have determined for it phases, until it returns [appearing] like the old date stalk.

Translation: Saheeh International

Tafsir

And the moon — read wa’l-qamaru in the nominative or wa’l-qamara in the accusative; and it may be in the accusative because of a following verb that governs it We have determined it with respect to its course to run in phases — twenty eight phases in twenty eight nights of every month; …

Excerpt from Tafsir al-Jalalayn, commentary on 36:39, via Quran.com. The reader has the full commentary and 9 more tafsirs.