Where from?

[Nevtalathiel]

Can anyone tell me where this verse comes from?

An Elven-maid there was of old,
A shining star by day:
Her mantle white was hemmed with gold,
Her shoes of silver-grey.

A star was bound upon her brows,
A light was on her hair
As sun upon the golden boughs
In Lórien the fair.

Her hair was long, her limbs were white,
And fair she was and free;
And in the wind she went as light
As leaf of linden-tree.