I fondly remember singing this beautiful song in two-part harmony in seventh grade. Here are the complete lyrics as I remember them:

Now the green leaves grow,
Tomorrow I must go,
Today I shelter here,
That none may know.

In flowers and in garlands
I'm clothed today,
Tomorrow without shoe or staff
I go away.

This must be my farewell,
I will not come again,
Nor shall I leave a footprint
Light as snow or rain.

Friends I must forget
Will think of me and say
A pater noster
At the end of day.

Amen, amen, amen,
Those words will stand and keep
Their watch and guard around me
Where I sleep.

Amen, amen, amen,
Those words will stand and keep
Their watch and guard around me
Where I sleep.

If anyone knows the origins of this song, please let me know. Thank you.