Der Tag der ist so freudenreichaller Kreature,denn Gottes Sohn vom Himmelreichüber die Naturevon einer Jungfrau ist geborn;Maria, du bist auserkorn,daß du Mutter wärest.Was geschah so wunderlich?- Gottes Sohn vom Himmelreichder ist Mensch geboren.Ein Kindelein so löbelichist uns geboren heutevon einer Jungfrau säuberlichzu Trost uns armen Leuten;wär uns das Kindlein nicht geborn,so wärn wir allzumal verlorn,das Heil ist unser aller.Ei, du süßer Jesu Christ!daß du Mensch geboren bistbehüt uns vor der Hölle.Als die Sonn durchscheint das Glasmit ihrem klaren Scheine,und doch nicht versehret das,so merket allgemeine,zu gleicher Weis geboren wardvon einerJungfrau rein und zartGottes Sohn der werthe.In ein Kripp ward er geleit,große Marter für uns leidthie auf dieser Erden.Die Hirten auf dem Felde warnerfuhren neue Mährevon den englischen Scharn,wie Christ geboren wäre,ein König übr all König groß;Herod' die Red gar sehr verdroß,aussandt er seine BotenEi, wie gar ein flasche Listerdacht er wider Jesum Christ,die Kindlein ließ er tödten.Verdeutschung des Hymnus: Dies est laetitiae. Schon vor der Reformation in Gebrauch.
My prose translation
The day that is so joyfulFor all creaturesFor God's Son from Heaven,Higher than nature,Of a virgin is born.Mary, you are chosenThat you would become a mother.What is so strange that happened?- God's Son from Heaven,He is born as a human being.A little child so praise worthyIs born for us to-dayOf a virgin pureFor the comfort of us poor people;Were the little child not born to us,We would be lost for all timeThe salvation is for us all.O, You sweet Jesus Christ!That You are born as a human being,Protect us from hell.As the sun shines through the glassWith its clear lightAnd is not dimmedSo everyone noticesIn the same way was bornOf a virgin pure and gentleGod's dear Son.To a manger He was directedGreat torment for us sufferedHere on this earth.The shepherds in the field wereTold new storiesBy the angelic hosts,How Christ would be bornA great King over all kings;The talk greatly annoyed Herod,He send out his messengersOh, what a false trickHe devised against Jesus Christ,He had the little children put to death.German translation of the hymn The Day Is of Joy. In use even before the Reformation.
I'm not entirely sure that I translated "Mähre" correctly. All translations I could find for this word had to do with horses, which obviously doesn't fit the context. I think it's an-other instance of older German words being spelt differently; a modern rendering would be Mär (Mären in the plural).
It's a bit unclear what "groß" in the line "ein König übr all König groß" is modifying. I took it as a post-positive adjective modifying the first "König" (A great King over all kings), but I think it could also modify the second "König" (A King over all great kings). The second "König" is plural, but the -e of Könige (and alle) is omitted, apparently for metrical reasons.
The hymn appears as "Hail the Day So Rich in Cheer" in The Lutheran Hymnal (#78), although this contains only the first two verses. The Gesangbuch notes that this text is sung to "its own melody," and this is also what it's paired with in TLH: