How does the following quotation relate to Sir Gawain and the Green Knight and other medieval literature: "In serving each other we become free"?

Although this quote applies loosely to the chivalric code
put forth by the legendary King Arthur and the Knights of the Round Table, it is not
contained within Sir Gawain and the Green Knight.  I say "loosely"
because, from what I understand, it can only be found within the context of the movie
First Knight.

Spoken by King Arthur to
Lancelot and inscribed upon the famed "round table," this quote exemplifies both the
loyalty and the valor of this medieval code.  Therefore, in regards to literature,
perhaps we can relate this quote best to famous pieces of literature such as
Idylls of the King, Morte d'Arthur and
Sir Gawain and the Green Knight which most definitely deal with the
code of chivalry.

Just because King Arthur is legendary and
this quote imagined doesn't mean that we can't appreciate it for what it's worth,
however. It deals with loyalty, certainly an admirable quality.  These Knights of the
Round Table certainly had loyalty to God, their country, and their king above all else. 
The knights were there to serve and, in so doing, keep Christendom free from the enemy. 
Protecting and serving the community is still valued even in society today.  In that, we
can say that this code of chivalry is certainly not "dead," as some people
claim.

The code of chivalry had some particular indicators
of nobility, which was still able to be achieved even through war that they considered
to be the "serving each other" in the quote above.  No one should ever attack from the
back.  No torture was allowed.  No unprepared opponent should be set upon.  Above all,
justice should be administered.

For example in
Sir Gawain and the Green Knight chivalry can easily be found in the
following lines:

readability="8">

Now take care, Sir Gawain, / That your courage
wax not cold / When you must turn again / To your enterprise
foretold.

Of course, Sir
Gawain takes up his quest and is eventually rewarded, ... as is King Arthur in
Morte d'Arthur. Chivalry peppers this text and summed up nicely in
the following quote:

readability="6">

Do after the good and leave the evil, and it
shall bring you to good fame and
renown.

Ironically, if you
change one little word of the quote within your question to read "by serving each other
we become free," I have heard it applied to everything from football, to Tibetan and
Mongolian wisdom, and even within the confines of Christianity to exemplify the best way
to live one's life in Christ!