When you translate it to English you see that the song is about death and the journey to heaven.
Translation:
Merciful Jesus 4x
Father, who takes away the sins of the world.
Grant them rest 2x
Merciful Jesus 4x
Father, who takes away the sins of the world.
Grant them rest 2x
Lamb of god 4x
Father, who takes away the sins of the world.
Grant them rest 2x
Everlasting 2x
Rest.
When you translate it to English you see that the song is about death and the journey to heaven.
Translation: Merciful Jesus 4x Father, who takes away the sins of the world. Grant them rest 2x Merciful Jesus 4x Father, who takes away the sins of the world. Grant them rest 2x Lamb of god 4x Father, who takes away the sins of the world. Grant them rest 2x Everlasting 2x Rest.