In his letter to the Galatians, Paul points out the difference between giving one's ultimate adherence to the Jewish Law or Christ. He does this by reinterpreting the Old Testament images of the two wives of Abraham, namely, Hagar and Sarah, and their respective sons, Ishmael and Isaac.

Hagar represents the Covenant of Mount Sinai, which is linked to the legal demands of the Torah. Like Hagar, who was a slave of Abraham, those adhering only to the Mosaic Covenant are "slaves" to the law. In comparison, Sarah represents the Abrahamic Covenant which is entirely free from the Torah's legal prescriptions. Christians are part of this covenant and are not "slaves" like Hagar or Ishmael, but "free" children of God because of Christ.

In the gospel, Jesus responds to the question by the Jewish authorities who had asked for a sign to show that his power is not demoniac. The Pharisees and scribes, religious leaders and experts of the Torah, had accused Jesus of getting his power from Satan. Jesus points out that he himself is the sign. He compares himself to Jonah; when Jonah came, the people of Nineveh reformed their lives. Jesus too has come with a message of salvation, if only the people will heed it. If they do not adhere to his message, they will see Jesus' liberating power move away from them to others who are far off.

So, to what or to whom do you give your ultimate adherence to? Are you a "slave" to the things of the world or a "free" child of God?