Marie (since 1581 called "Marie de France" [Lais 7]), "Prologue," lines 9-27

9 custume fu as anc‹ens,
10 ceo tes[ti]moine Prec‹ens,
11 es livres ke jadis feseient
12 assez oscurement diseient
13 pur ceus ki a venir esteient
14 e ki aprendre les deveient,
15 k'i pessent gloser la lettre
16 e de lur sen le surplus mettre.
17 li philesophe le saveient
18 e par eus memes entendeient,
19 cum plus trespasserunt le tens,
20 plus serreient sutil de sens
21 e plus se savreient garder
22 de ceo k'i ert, a trespasser.
23 ki de vice se volt defendre
24 estud‹er deit e entendre
25 e grevos'ovre comencier:
26 par [ceo] se puet plus esloignier
27 e de grant dolur delivrer.

It was customary for the ancients, in the books which they wrote (Priscian testifies to this), to express themselves very obscurely so that those in later generations, who had to learn them, could provide a gloss for the text and put finishing touches in their meaning.  Men of learning were aware of this and their experience had taught them that the more time they spent studying texts the more subtle would be their understanding of them and they would be better able to avoid future mistakes.  Anyone wishing to guard against vice should study intently and undertake a demanding task, whereby one can ward off and rid oneself of great suffering.  (Prose Translation, Glyn Burgess and Keith Busby)

 Among the ancients it was the tradition
(On this point we can quote Priscian)
When they wrote their books in the olden day
What they had to say they'd obscurely say.
They knew that some day others would come
And need to know what they'd written down;
Those future readers would gloss the letter,
Add their own meaning to make the book better.
Those old philosophers, wise and good,
Among themselves they understood
Mankind, in the future tense,
Would develop a subtler sense
Without trespassing to explore
What's in the words, and no more.
Whoever wants to be safe from vice
Should study and learn (heed this advice)
And undertake some difficult labor;
Then trouble is a distant neighbor--
From great sorrows one can escape.  (Verse Translation, Judith Shoaf, http://web.english.ufl.edu/exemplaria/marie/prologue.pdf)