Greek Key Terms:
Context: Paul quotes Genesis 21:10 verbatim (LXX): "Cast out the slave woman and her son, for the slave woman's son will never share in the inheritance with the free woman's son." This is the climactic application of his Hagar-Ishmael typology—the Judaizers who preach circumcision and law-keeping must be expelled from the church. Paul then concludes: "Therefore, brothers, we are not children of the slave woman, but of the free woman" (v. 31).
OT-to-OT Development:
Connections:
Christological Connection: The command to "cast out the slave woman and her son" points to the final judgment where Christ will separate sheep from goats (Matthew 25:31-46). Just as Ishmael (flesh-born) was permanently excluded from Abraham's household, those trusting in works (Matthew 7:22-23, "many will say to me on that day, 'Lord, Lord, did we not...'") will be excluded from the kingdom: "Depart from me, I never knew you" (Matthew 7:23). The exclusion is absolute: "will never share in the inheritance." Conversely, those who are "in Christ" (2 Corinthians 5:17) by faith are "children of the free woman" (Galatians 4:31) and will inherit eternal life. The Hagar-Ishmael trajectory teaches that salvation is exclusively by grace through faith in Christ—no human works can secure or supplement it. Those who add works to grace will hear the final "Cast out," while those trusting in Christ alone will hear "Come, you who are blessed by my Father, inherit the kingdom" (Matthew 25:34).
Related Trajectory Tables:
Connection Method(s): Typology (Providential, Backward-Looking), Contrast — The permanent exclusion of Ishmael from the inheritance ("will never share") prefigures the final judgment's absolute separation between those trusting in works and those trusting in Christ, establishing that salvation is exclusively by grace through faith.
Trajectory Table: 068 - Hagar and Ishmael (Children of the Flesh)