This short parable appears each of the synoptic gospels
but, in each, presents a slightly different message.
The differences are in themselves a parable:

Luke's Gospel Luke (cl)

Luke's version advocates the clarity of God's message.
Divine truth is available to all.
It doesn't take years of study,
nor do we have to plough through the Bible,
or through other theological text.
God's truths are out in the open,
if we just look for them.
But watch out if you fail to take this opportunity.
It won't come again.

Mark's Gospel Mark (cl)

Mark's Gospel includes an extra onus
on those who have received this information.
They will be judged more strictly than those who have not.
Be careful what you hear, could be the message, in Mark,
because you will be judged on how you use the information
either to grow or to fall away.

Matthew's Gospel Matthew (cl)

Matthew's Gospel gives yet another slant.
You are the light for the whole world.
Don't hide yourself away.
Your light must shine
Others must see the good things that you do,
and thereby realise the reality of God.

The Gospels would seem to have on a common baseline,
which has been used to preach a variety of messages
much as preachers use Bible texts today.

The variations in the parable are themselves a parable
 These stories are second or third hand accounts of what Jesus did and said,
often written down with a bias that reflects particular local concerns,
or the intentional thrust of particular teachers.
All have, of course, suffered the ravages of time and copyists.

It is in vain that our theologians sift the meaning
from the individual words of the Bible, or even the separated stories.
Yet the thrust of God's message is clearly written in scripture.
Even in this short passage, which twice follows the tale of the Sower,
we can see a common thread:
that God's truth is available and that we are called not to misuse it.

The corollary might be that we have done so in many different ways
(slavery, sexism, conquest, individualism....)
and need to find our way out of the mire, somehow.

Yet there are too many vested interests in the clerical empire
for the church to have a ready exit strategy from its dilemma
and we have no leverage with which to move the mountain.
The Reformation took us a step upon the way,
but we have further to go if we are to cleanse the church.