This text comes from The Poetical Works of Robert Burns, a historical songbook transcribed on Wikisource and reproduced from the pinned revision linked below.
O were my love yon lilac fair,
Wi' purple blossoms to the spring;
And I, a bird to shelter there,
When wearied on my little wing;
How I wad mourn, when it was torn
By autumn wild, and winter rude!
But I wad sing on wanton wing,
When youthfu' May its bloom renew'd.
O gin my love were yon red rose
That grows upon the castle wa',
And I mysel' a drap o' dew,
Into her bonie breast to fa'!
Oh, there beyond expression blest,
I'd feast on beauty a' the night;
Seal'd on her silk-saft faulds to rest,
Till fley'd awa' by Phœbus' light.