This text comes from Songs of Innocence and of Experience (1826), a historical songbook transcribed on Wikisource and reproduced from the pinned revision linked below.
Once a dream did weave a shade,
O'er my Angel-guarded bed,
That an Emmet lost its way
Where on grass methought I lay.
Troubled wilderd and forlorn
Dark benighted travel-worn,
Over many a tangled spray,
All heart-broke I heard her say,
O my children! do they cry,
Do they hear their father sigh,
Now they look abroad to see,
Now return and weep for me.
Pitying I drop'd a tear;
But I saw a glow-worm near:
Who replied, What wailing wight,
Calls the watchman of the night.
I am set to light the ground,
While the beetle goes his round:
Follow now the beetles hum,
Little wanderer hie thee home.