Vespers

The Vespers evening prayer has roots in the evening sacrifice and prayers offered in the Jewish Temple, which were a way to mark the end of the day and offer thanksgiving. Early Christians, influenced by Jewish customs, adopted evening prayers as part of their daily worship, as noted in the "Didache," a church manual from around 100 AD.

Over time, especially during the 4th, 5th, and 6th centuries, cathedral choirs and monastic orders formalized the structure of Vespers, incorporating psalms, readings, and hymns. 

A fixed hymn for Vespers in the Byzantine rite, and one of the earliest Christian hymns outside the Bible is "Phos Hilaron" ("Hail Gladdening Light"), dating back to the 3rd or 4th century. Phos: (φῶς) is the Greek word for light. Hilaron: (ἱλαρόν) is an adjective meaning joyful, gladsome, gracious, or gentle. It's still used in Orthodox Vespers today. Below is a link to a popular Byzantine English rendition:

In the Roman Rite, Vespers highlights the canticle of Mary, the Magnificat.