Genesis 17:19 is where God names Isaac as the covenant heir. Sarah's demand to expel Ishmael enforces what God already declared: the promise runs through Isaac alone.

In Genesis 17:21, God explicitly excludes Ishmael from the covenant, designating Isaac alone. Sarah's insistence is grounded in this prior divine distinction.

Genesis 25:6 shows Abraham later sending away concubines' sons, fulfilling the demand made here.

In Genesis 24:36, Abraham's servant confirms Isaac received everything — the fulfillment of what Sarah insisted upon: that Isaac alone would be heir.

Genesis 25:5 confirms Abraham gave all he had to Isaac — the direct fulfillment of Sarah's demand that only her son would inherit.

Genesis 16:1 introduces Hagar as Sarah's maidservant — the backstory that makes Sarah's demand here explicable. It frames who this 'bondwoman' is.

Genesis 25:9 shows Isaac and Ishmael together burying Abraham — revealing a reconciliation between the brothers despite the earlier separation.

Genesis 30:4 shows Rachel giving her maid to Jacob to bear children — the same surrogacy pattern Sarah used with Hagar, echoing the dynamics of 21:10.

Jesus directly alludes to this event: the slave's son does not remain in the household forever, but the true son by promise does — Ishmael's exile in a sentence.

In Galatians 4:22-31, Paul directly references this event, using Hagar and Sarah as an allegory for two covenants — slavery under law versus freedom through promise.

Galatians 4:30 directly quotes this verse about driving out the slave woman, applying the story as an allegory for the two covenants.

In Galatians 3:18, Paul argues the inheritance comes through promise, not law — matching Sarah's insistence that Isaac, the promised child, alone inherits.

In Galatians 4:7, Paul declares believers are heirs as sons, not slaves — directly echoing Sarah's distinction between her son and the bondwoman's son.

Galatians 3:29 defines true inheritance through faith in Christ, not physical lineage — contrasting with Ishmael's displacement here.