Lobt Gott, ihr Christen allzugleich,in seinem höchsten Thron,der heut aufschleußt sein Himmelreich,und schenkt uns seinen Sohn. :,:Er kömmt aus seines Vaters Schoßund wird ein Kindlein klein;er liegt dort elend, nackt und bloßin einem Krippelein. :,:Er aüßert sich all sein Gewalt,wird biedrig und gering,und nimmt an sich eins Knechts Gestalt,der Schöpfer aller Ding. :,:Er liegt an seiner Mutter Brust,ihr Milch ist seine Speis,an dem die Engel sehn ihr Lust,denn er ist Davids Reis, :,:Das aus seim Stamm entsprießen sollt,in dieser letzten Zeit,durch welchen Gott aufrichten wolltsein Reich, die Christenheit. :,:Er wechselt mit uns wunderlich,Fleisch und Blut nimmt er an,und gibt uns in seins Vaters Reichdie klare Gottheit dran. :,:Er wird ein Knecht und ich ein Herr,das mag ein Wechsel sein!Wie könnt es doch sein freundlicher,das Herze-Jesulein? :,:Heut schleußt er wieder auf die Thürzum schönen Paradeis;der Cherub steht nicht mehr dafür.Gott sei Lob, Ehr und Preis. :,:Nikolaus Hermann, 1560.
My prose translation:
Praise God, you Christians altogether,On His holy throne,Who to-day opens His heavenly kingdom,And gives us His Son. :,:He comes out of His Father's bosomAnd becomes a small child;He lies there miserably, naked and bareIn a manger. :,:He shows all of His power,Becomes humble and small,And takes on Himself the form of a servant,The Creator of all things. :,:He lies on His mother's breast,Her milk is His food,In Whom the angels see their desire,For He is David's branch, :,:That should spring from his lineageIn this last time,Through which God wants to establishHis kingdom, Christianity. :,:He exchanges with us wonderfully.He takes on flesh and bloodAnd in His Father's kingdom gives us toThe clear Godhead. :,:He becomes a servant, and I a lordThat [such] an exchange may be!How can it be friendlier,The heart of Jesus? :,:To-day He opens again the doorTo the beautiful paradise;The cherub no long stands before it.To God be extolment, honor, and praise. :,:Nikolaus Hermann, 1560.
The line "und nimmt an sich eins Knechts Gestalt" ("And takes on Himself the form of a servant") comes from part of Philippians 2:7: "nahm Knechtsgestalt an" ("taking the form of a servant").
The only translation that my dictionary provides for "Reis" (the only translation that fits this context, at least) is "twig." I took this a bit further and translated it as "branch" because it seems to be a reference to Isaiah 11:1: "There shall come forth a shoot from the stump of Jesse, and a branch from his roots shall bear fruit."
The eighth verse refers to Genesis 3:24: "He [God] drove out the man, and at the east of the garden of Eden he placed the cherubim and a flaming sword that turned every way to guard the way to the tree of life." In the hymn text, however, it's a single cherub, not cherubim.
The phrase "Lob, Ehr und Preis" was a bit difficult to translate because "Lob" and "Preis" both mean "praise." For some variation, I went with "extolment," although it's not a very common word.
This hymn appears as "Praise God the Lord, Ye Sons of Men" in The Lutheran Hymnal (#105) and as "Let All Together Praise Our God" in Lutheran Worship (#44) and The Lutheran Service Book (#389). In all of these, and as the Gesangbuch notes, the text is sung to "its own melody." Here's the TLH arrangement:
I'm still not sure what :,: means, but here at least, it seems to indicate a repetition of the last line.