Genesis is a good place to appreciate what God sees as most important. At the end of the book, in Genesis 49, Jacob is blessing his sons, and, in verse 10, the Messianic promise is passed unto Judah. The book details the line of God’s promise and why certain people are chosen or passed over as God maintains that line. Returning to the beginning of the book provides a key for all that follows. In Genesis 3:15, the promise of enmity between the seed of woman and the devil is first made.
Immediately, in Genesis 4 a contrast is drawn between Cain and Able. Genesis 6 draws a contrast between Noah and the sinful population around him. This contrast continues, and, in Genesis 21, we see this conflict between Ishmael and Isaac. This strife between the devil’s followers and the seed of the promise until it culminates with Christ’s crucifixion and victory over death in the gospels.
The Seed of Promise
Genesis 12 records the multifold promise God makes to Abraham in which God promises the blessing of the world through Abraham’s seed. This term of seed repeats through the book, and, in Genesis 21, God makes it clear that the seed of promise will continue through Isaac. Isaiah 41:8 records God calling His people the seed of Abraham His friend. Also, Acts 3:25 has Peter and John focusing in on that same language, looking back to those promises made in Genesis. Galatians 3:16 then makes it clear that this singular see was to culminate in one, that is Christ.
In II Samuel 7, God makes reference to a seed of promise when David wishes to build God a great house of worship. In verse 13, God speaks of a sure household and throne for David. The prophets refer to this offspring as a branch of David, and Jeremiah 33:26 records God saying His promises to the seed of Abraham, Isaac, and David are as sure as day and night. In John 7:42, while Jesus is calling on those around Him to come and drink the water of life, the people question his lineage, whether or not he is of the seed of David. Romans 1:1 has Paul placing emphasis on this lineage while writing to Jews and Gentiles in Rome, and, in Revelation 22:16, Jesus Himself refers to the seed of David.
Ishmael and Isaac
Returning to Genesis 21, Sarah calls on Abraham to cast Hagar and Ishmael out of their household because of the animosity between the women and their children. Approximately fifteen years separate these children, and Ishmael is pictures as mocking of Isaac. The Hebrew gives the idea that Ishmael is playing as if he is the true heir of Abraham’s household rather than the baby Isaac, only recently weaned in Genesis 21. God validates Sarah’s concerns, and He tells Abraham to follow her advice to cast Hagar and Ishmael out.
Galatians 4:22 makes a parallel that Ishmael represents that which is carnal, and Isaac represents spirituality. In verse 28, Paul makes the connection that we are supposed to be trusting in the spiritual promises of God, and he speaks of the physical standing at enmity with the spiritual. The two cannot exist together. We cannot be spiritual while holding onto the physical. The conflict in Genesis 21 is a continuation of the conflict that begins in Genesis 3, and it foreshadows John 15:18.
A Shadow of Christ
Isaac is the only begotten son of Abraham and Sarah. He is the seed of promise through whom the nations will be blest, and God even calls on him to be sacrificed. Through Isaac, God sees Abraham’s love and commitment to God, and God demonstrates that love and commitment to us in not sparing His own Son. God gave up the culmination of the seed of promise for the sake of our sins, raised Him up, and sits Him down at the throne’s right hand. It all begins in Genesis.
lesson by Tim Smelser