“No man under Heaven can hurt him, whoever may try, / For nothing on earth, however uncanny, can kill him.” (line 225 - 226) “This might be a treasure indeed when the time came to take / The blow he had bargained to suffer beside the Green Chapel. / If the gift meant remaining alive, it might well be worth it” (line 228 - 230)
The lady continues to push for Gawain to take the sash but he refuses. She tells him that if he wears the sash, no man can hurt him during battle. Gawain realizes that this might be helpful for when he has to take the blow from the Green Knight.
Take this slash. It will protect you in battle.
“But you lacked a little, sir; you were less than loyal / But since it was not for the sash itself or for lust / But because you loved your life, I blame you less.” (lines 344-346)
The Green Knight and Sir Gawain then go out to fulfill their original promise. Sir Gawain's green slash causes the blow to not hurt him much. However, the Green Knight reveals to Sir Gawain that he knew he wore the green slash the entire time. Furthermore, he set up the whole thing with his wife to and found he was not a loyal knight.
“Remember our struggle here; recall to your mind / This rich token. Remember the Green Chapel.” (lines 375-376)
Sir Gawain admits to his faults and comes clean to the Green Knight. The Green Knight says to Sir Gawain that he is now clean of any faults and is essentially a new man. Furthermore, he tells Sir Gawain to remember the Green Chapel as a valuable lesson for him as a loyal knight in the future. Both the men then bid farewell and go on their separate ways.