“I will open my mouth in a parable. I will utter dark sayings of old,
which we have heard and known, and our fathers have told us.”
This is the Son of God talking through the prophet, stating that he will do two things at the same time. He will speak in parables, but with those parables, he will be repeating familiar stories that had been told in Israel for generations. When Jesus spoke of Jonah being in the whale’s belly for three days, he was doing this. The story of Jonah was a familiar story in Israel, but it was, at the same time, a parable of Jesus being in the “belly” of the earth for three days.
Jesus also spoke of Abraham, Moses, David, and others. All those ancient stories were familiar to Israel, but they were also mysteries, parables if you will, which no one had ever understood – not even Abraham, Moses, or David.
Jesus came to show us the knowledge of God. Part of that knowledge was that every ancient story had been designed by God as a parable of His hidden Son. The Son was God’s “second Adam”; he was Abraham's Isaac, the beloved sacrifice; he was Moses’ “prophet like unto me”; and he was the son of David who would sit on the throne forever. And he was the meaning behind countless other ancient stories as well.
From the foundation of the world, men of God had prophesied of the coming Son of God, but Jesus revealed that those men themselves were symbols of him. Their lives, directed by God, also prophesied of him. When Jesus told those ancient stories, it was the first time in history that they have been told the way they were intended by God to be understood.