Here’s some info about this hymn from hymnary.org:
As attested by Augustine in 372, as well as by other early writers, Ambrose wrote this hymn in Latin (“Veni, Redemptor gentium”) in the fourth century. The text appears in a number of eighth- and ninth-century manuscripts. Martin Luther (b. Eisleben, Saxony, Germany, 1483; d. Eisleben, 1546) translated this text into German in 1523 and included it in the Erfurt Enchiridia (1524). Consequently “Savior of the Nations” has become possibly the best known of the Lutheran Advent hymns. Various English translations are found in modern hymnals, many of which use, at least in part, William M. Reynolds’s translation from his Hymns, Original and Selected (1851).
Ambrose (b. Treves, Germany, 340; d. Milan, Italy, 397), one of the great Latin church fathers, is remembered best for his preaching, his struggle against the Arian heresy, and his introduction of metrical and antiphonal singing into the Western church. Ambrose was trained in legal studies and distinguished himself in a civic career, becoming a consul in Northern Italy. When the bishop of Milan, an Arian, died in 374, the people demanded that Ambrose, who was not ordained or even baptized, become the bishop. He was promptly baptized and ordained, and he remained bishop of Milan until his death. Ambrose successfully resisted the Arian heresy and the attempts of the Roman emperors to dominate the church. His most famous convert and disciple was Augustine. Of the many hymns sometimes attributed to Ambrose, only a handful is thought to be authentic.
Savior of the Nations, Come
Savior of the nations, come;
Virgin’s son, make here your home.
Marvel now, O heav’n and earth,
That the Lord chose such a birth.
Not by human power or seed
Did the woman’s womb conceive,
Only by the Spirit’s breath
Was the Word of God made flesh.
From the Father forth He came
Soon returning to the same.
Captive leading death and hell;
Let the song of triumph swell!
Christ laid down his majesty,
Passed through dark Gethsemane;
Though he left his Father’s home,
Christ now sits on God’s own throne.
Praise to God the Father sing,
Praise to God the Son, our King,
Praise to God the Spirit be
Ever and eternally.