This text comes from The Book of Scottish Song, edited by Alexander Whitelaw, a historical songbook transcribed on Wikisource and reproduced from the pinned revision linked below.
Once William swore the sacred oath,
That I my love had never weary;
And I gave him my virgin troth,
But now he's turn'd awa' frae Mary.
I thought his heart was link'd to mine,
So firm that it could never stray;
Yet, William, may that peace be thine,
Which thou hast ta'en frae Mary Gray.
I once was happy in his love,
No gloomy prospect made me dreary;
I thought that he would never rove,
But aye be faithfu' to his Mary.
Bright on me shone sweet pleasure's sun,
I sported in its gladdenmg ray;
But now the evening shades are come,
And soon will close round Mary Gray.
Yet, 'William, may no gloomy thought
Of my love ever make thee dreary;
I've suffer'd much—'twas dearly bought,—
Peace now has fled frae wretched Mary.—
And when some maid, more loved than me,
Thou lead'st to church on bridal day,
Perhaps the lowly grave you'll see,
Of poor neglected Mary Gray.