Weekdays
The distinguishing feature of the Midnight Office on weekdays is the reading of the Seventeenth Kathisma comprising Psalm 118, the longest Psalm in the Bible, in the First Part of the office. The troparia chanted in the First Part are the Troparia of the Bridegroom: "Behold, the Bridegroom cometh at midnight...", recalling the Parable of the Wise and Foolish Virgins. The first of these troparia is also solemnly chanted at Matins during Holy Week, from which the Matins service on these days derives its name of "Bridegroom Prayer."
Read more about this topic: Midnight Office