The people who walked in darkness
have seen a great light;
those who lived in a land of deep darkness—
on them light has shined.
So we have the prophetic message more fully confirmed. You will do well to be attentive to this as to a lamp shining in a dark place, until the day dawns and the morning star rises in your hearts.
~2 Peter 1:19
When they had kindled a fire in the middle of the courtyard and sat down together, Peter sat among them. Then a servant-girl, seeing him in the firelight, stared at him and said, “This man also was with him.” But he denied it, saying, “Woman, I do not know him.”
~ Luke 22:55-57
There are references to light in all three of the readings for the Tuesday of the Third Sunday of Advent.
In the first reading from Isaiah, we have light shining on people who have been in darkness, and from the context, it is understood that this is a good thing. The world is coming into joy, the rods of the oppressors have been broken and a boy child has come to bring peace to the throne of David and establish justice and righteousness for ever. This light is a joyful light of revelation and removal oppression.
In second Peter, we have passage in a letter that insists that the story of Jesus, and in particular God claiming Jesus as God's son, really happened on the holy mountain. It was not a 'cleverly devised myth'. In this case the completed prophecy, Jesus's coming, has been confirmed by the eyewitness. The fact that the prophecy has been fulfilled is to be considered as a lamp in a dark place. This struck me, because I have used an oil lamp when the power was out and when I have a single lamp burning in a dark room I cannot help but be aware of it. Unlike the steady ambient light electricity provides, an oil lamps flame glows as a point in the dark and flickers like a living thing in the moving air of a room. The idea of the lamp in the dark place seems to me then, to be something so obvious that it cannot be overlooked. It is something that would either take an effort of will to ignore or that one could become used to after it was lit and only think about it when it went out. The coming of Jesus is the light in the darkness that I should not take for granted.
In the Gospel of Luke, the light is a fire that is lit in the courtyard of the high priest's house. It is by this light that Peter is recognized by a woman and two men as a follower of Jesus and it is in that light that Peter denies his relationship to Jesus three times. The cock crows, Peter realizes what he has done, and the sun can rise-- giving a greater light than that of the fire. The light of this fire is not the joyful light of Isaiah or the persistent light of a prophecy fulfilled.
In this crowd, he is the only one who knows of Jesus's prophecy that Peter will deny him three times this night. When he hears the cock crow and realizes what he has done Peter weeps bitterly. He holds himself to account. The light of the fire he was revealed to others as a follower of Jesus and in that same light he was revealed to himself in a way that he does not like.
The great thing about Peter is that he does not accept this failure on his part. He owns up to it (otherwise we wouldn't have the story). He is disappointed in himself, but, while he denies Jesus those three times, he goes on to follow Jesus to the cross, death, and resurrection. Peter spends the rest of his life sharing both the life-story and the words of Jesus. The firelight of his denial galvanizes him into action. The dawn-light of weeping bitterly is transformed into a lifetime of service.
All bible quotes are from either the NRSV or RSV text at Bible Gateway