Riddle Poem by Anna Laetitia Barbauld

From rosy bowers we issue forth,
From east to west, from south to north,
Unseen, unfelt, by night, by day,
Abroad we take our airy way:
We foster love and kindle strife,
The bitter and the sweet of life:
Piercing and sharp, we wound like steel;
Now, smooth as oil, those wounds we heal:
Not strings of pearl are valued more,
Or gems enchased in golden ore;
Yet thousands of us every day,
Worthless and vile, are thrown away.
Ye wise, secure with bars of brass
The double doors through which we pass;
For, once escaped, back to our cell
No human art can us compel.