The hymn of the day, Hark! A Thrilling Voice Is Sounding (LSB 345), tells of the work of John the Baptist. His voice is thrilling to believers, for his voice heralds the coming of our Savior, Jesus.
As is the case with several carols and anthems for Advent and Christmas in current common use, this text and tune with its descant have gained greater acceptance and use in the Church through their inclusion in a recording of Advent Lessons and Carols by the choir of King’s College, Cambridge.
The hymn is found in two 10th century sources. The hymn abounds with scripture references; indeed every line in the Latin original can reasonably be associated with a passage from scripture, if not a direct reference, at least a reflection. The translation by Edward Caswall, which appeared in his Lyra Catholica  preserves most of the biblical references.
The word “hark” is a perfectly good word but for some reason it seems to appear mostly at this time of year in Advent and Christmas hymns. Defined as “to listen carefully, to be attentive,” it surely is the correct word for our waiting and watching during the Advent season.
Composed by William Henry Monk, first appeared in the Parish Choir, 1850, and in the first addition of Hymns: Ancient & Modern  for which Monk served as musical editor and was the person who suggested the title for that historic collection. The tune’s title is thought to refer to Walter de Merton, founder of Merton College, Oxford, England.
Prayer at nightfall: We praise and thank You, O God, for You are without beginning and without end. Through Christ You are the creator and preserver of the whole world; but above all, You are His God and Father, the giver of the Spirit, and the ruler of all that is, seen and unseen. You made the day for the works of light and the night for the refreshment of our weakness. O loving Lord and source of all that is good, mercifully accept our evening sacrifice of praise. As You have conducted us through the day and brought us to night's beginning, keep us now in Christ; grant us a peaceful evening and a night free from sin; and at the end bring us to everlasting life through Christ, our Lord; through Him be glory, honor, and power to You in the Holy Spirit now and always forever and ever.
 An evening prayer, Lutheran Service Book © 2006 Concordia Publishing House, St. Louis