17:78

"Establish the Prayer at the sun's decline until the darkness of the night; and the Qur'an of dawn, for the Qur'an of dawn is witnessed."

footnote no. 556 from the Majestic Qur'an:

To establish the prayer is to perform the ritual prayer regularly at the time it is due, completing all its parts in the most excellent manner. The ritual prayer, being one of the five pillars of Islam, allows of no complacency, neglectfulness, or distraction. The time from when the sun beings to decline till when the night grows dark includes four obligatory prayers: midday, afternoon, sunset, and night. The Qur'an makes special mention of the dawn prayer which is the prayer where the recitation of the Qur'an is most prolonged, hence its name: the Qur'an of dawn. At that time the angels of the night have not ascended yet and the angels of the coming day have descended; both witness the prayer and testify to this before Allah.