"That he dares to stoutly exchange one stroke for another, I shall let him have as my present this lovely gisarme, This ax, as heavy as he’ll need, to handle as he likes, And I will abide the first blow, bare-necked as I sit." (67-70)
The Green Knight came to King Arthur's knights and challenged them to slice his head off.
"I’d be deeply honored to advise you before all the court;For I think it unseemly, if I understand the matter, That challenges such as this churl has chosen to offer Be met by Your Majesty..." (124-127)
Arthur wanted to accept the Green Knight's challenge but Gawain didn't think it right of the king to have to do the task so he insisted that he do it.
"The sharp of the battleblade shattered asunder the bones And sank through the shining fat and slit it in two, And the bit of the bright steel buried itself in the ground." (149-151)
Gawain accepts the challenge of the Green Knight and cuts his head off but the green knight grabs his head and carrying it in his arms he leaves on his horse.
"As long as he keeps it looped around him, No man under Heaven can hurt him, whoever may try, For nothing on earth, however uncanny, can kill him.” (224-226)
Gawain is making his way to the green castle and he comes upon a nice castle and the king invited him to stay with him and his wife for a little. His wife makes moves on Gawain and trys to give him gifts that he continues to regret until he is offered a gift that could save his life.
Sir Gawain went to meet the green night and found him in a rugged place with only the sound of a sharpening blade in the background. Then the Green Knight did a fake swing which Gawain flinched at then He did the real swing.
"He raises that ax up lightly and flashes it down, And that blinding bit bites in at the knight’s bare neck— But hard as he hammered it down, it hurt him no more Than to nick the nape of his neck, so it split the skin; The sharp blade slit to the flesh through the shiny hide, And red blood shot to his shoulders and spattered the ground." (289-294)
The Green Knight explains that he was testing the quality of Gawain and Gawain turns out to be very noble and the Green Knight spares his life because of this.
“Whatever harm I’ve had, I hold it amended Since now you’re confessed so clean, acknowledging sins And bearing the plain penance of my point; I consider you polished as white and as perfectly clean As if you had never fallen since first you were born." (367-371)