The lyrics are by Ruckert:
Nun will die Sonn' so hell aufgehn,
Als sei kein Ungluck die Nacht geschehn!
Das Ungluck geschah nur mir allein!
Die Sonne, sie scheinet allgemein!
Du musst nicht die Nacht in dir verschraenken,
Musst sie ins ew'ge Licht versenken!
Ein Laemplein verlosch in meinem Zelt!
Heil sei dem Freudenlicht der Welt!
From the first Kindertotenlieder. Beautiful...my rough translation (you can probably find a better one on the internet somewhere, but here's mine):
Now the sun will rise as brightly,
As if no misfortune had happened in the night!
That misfortune has fallen on me alone.
The sun, it shines for everyone.
You mustn't keep the night inside you,
You must immerse it in light eternally!
A small lamp has been extinguished in my household;
Light of joy in the world, be welcome.
Oh, Mahler!