Galatians 4:22-24, 26-27, 31 -- 5:1
Jonah just walked through the city of Nineveh, one of the wickedest cities in all of history, and told them it would be destroyed. They repented in sackcloth and ashes, with fasting. Jesus walked through Jerusalem, the holy city, and told them it would be destroyed. They killed him. Jesus begins with the stories that the people have known their whole lives to show them how they are failing now.
St. Paul also begins with a story from the Old Testament. When Abraham and Sarah were not able to conceive, they used a surrogate mother, the slave of Sarah named Hagar. Hagar has a son, but Sarah hates her for it. Then Sarah finally has a son and kicks Hagar and her son out of the house. St. Paul says that this story is an allegory for us. As it really happened, Hagar was a good person who was mistreated, but in the allegory each person just stands for a concept. Hagar was an Egyptian slave. Sarah was the wife, a free woman. Hagar became pregnant easily, in the normal way. Sarah became pregnant only after decades of trying, only after God made a promise that she would have a son. Hagar symbolizes how Abraham tried to take control of the situation and make things happen by his own power. Sarah symbolizes waiting for God to fulfill his promise in the right time. Christ freed us, but we right now are like Abraham, waiting for God to fulfill what he has promised.
Do we trust God? Will we wait for the happiness he promised, or will we try to reach out and grab whatever we can provide for ourselves? The lesson of the allegory is that the son of a slave is still a slave. Abraham would have gladly handed over his house to his first son, Ishmael, but when the true son is born, Ishmael is kicked out by Sarah, proving that all along Hagar and Ishmael were nothing more than slaves. The happiness of sin seems like it is real, and while it is the only happiness we can have, we accept it, but all along it has always been slavery. When the true happiness of heaven is revealed, we would gladly forget about the sin. Compared to what is coming, the fleeting happiness of pleasure or possessions is nothing, but we will be enslaved by them if we choose.