The words are different from the original (Child) version but this is a very close approximation of the song as performed by Sandy Denny.
"I forbid you maidens all that wear gold in your hair
To travel to Carterhaugh, for young Tam Lin is there
None that go by Carterhaugh but they leave him a pledge
Either their mantles of green or else their maidenhead"
Janet tied her kirtle green a bit above her knee
And she's gone to Carterhaugh as fast as go can she
She'd not pulled a double rose, a rose but only two
When up then came young Tam Lin, says, "Lady, pull no more"
"And why come you to Carterhaugh without command from me? "
"I'll come and go", young Janet said, "and ask no leave of thee"
Janet tied her kirtle green a bit above her knee
And she's gone to her father as fast as go can she
Well, up then spoke her father dear and he spoke meek and mild
"Oh, and alas, Janet," he said, "I think you go with child"
"Well, if that be so," Janet said, "myself shall bear the blame
There's not a knight in all your hall shall get the baby's name
For if my love were an earthly knight, as he is an elfin grey
I'd not change my own true love for any knight you have"
So Janet tied her kirtle green a bit above her knee
And she's gone to Carterhaugh as fast as go can she
"h, tell to me, Tam Lin," he said, "hy came you here to dwell? "
"The queen of fairies caught me when from my horse I fell
And at the end of seven years she pays a tithe to hell
I so fair and full of flesh and feared it be myself
But tonight is Halloween and the fairy folk ride
Those that would let true love win at Mile's Cross they must bide
So first let pass the horses black and then let pass the brown
Quickly run to the white steed and pull the rider down
For I'll ride on the white steed, the nearest to the town
For I was an earthly knight, they give me that renown
Oh, they will turn me in your arms to a newt or a snake
But hold me tight and fear not, I am your baby's father
And they will turn me in your arms into a lion bold
But hold me tight and fear not and you will love your child
And they will turn me in your arms into a naked knight
But cloak me in your mantle and keep me out of sight"
In the middle of the night she heard the bridle ring
She heeded what he did say and young Tam Lin did win
Then up spoke the fairy queen, an angry queen was she,
"Woe betide her ill-far'd face, an ill death may she die"
"Oh, had I known, Tam Lin,' she said, "what this night I did see
I'd have looked him in the eyes and turned him to a tree"