Paul continues his argument that salvation is by grace and not by law. He does this through a legal and Old Testament illustrations.
Paul’s Illustrations
A. The Legal Illustration
1. The Roman father and his son, vv. 1-2
a. The frustration, v. 1: Until he comes of age, the son can enjoy very little of his father’s estate.
b. The freedom, v. 2: Upon coming of age, the son can enjoy all of his father’s estate.
2. The Redeemer’s Father and the Father’s children, vv. 3-7
a. The frustration, v. 3: While under the law, they enjoyed very little of the Father’s estate.
b. The freedom, vv. 4-7: Upon coming of age (effected by Christ’s death), they can enjoy all of their Father’s estate.
B. The Old Testament Illustration, vv. 21-31: The differences of Hagar and Sarah illustrate the difference between Mosaic law and the grace of God.
1. Hagar
a. She was a slave, vv. 21-22a.
b. Her marriage to Abraham was fleshly directed, v. 23a.
c. Her son, Ishmael, was naturally born, v. 24.
d. Their son was not considered Abraham’s rightful heir, vv. 30-31a.
e. She represents to earthly Jerusalem, v. 25.
2. Sarah
a. She was a free woman, v. 22b.
b. Her marriage to Abraham was spirit directed, v. 23b.
c. Her son, Isaac, was supernaturally born, v. 27.
d. This son was persecuted by Ishmael, v. 29b.
e. Her child was considered Abraham’s rightful heir, v. 28.
f. Sarah represents the new covenant, v. 27.
g. She represents the heavenly Jerusalem, v. 26.
Paul’s Inquiry
A. The rebuke, vv. 8-11: Paul faults them for their return to legalism.
B. The review, vv. 12-18
1. Paul reminds them that they once were his friends, vv. 12-15.
2. Paul wants to know if they are now his foes, vv. 16-18.
C. The rebirth, vv. 19-20: Paul will suffer the pains of childbirth until Christ is fully developed in them.