I. AN OUTLINE OF THE CHAPTERS 10:19-12:29
The Superiority of Believers' Privileges
Faith that Saves, 10:19-25 (taking action: exhortation)
Faith that's Disingenuous, 10:26-31 (the road backward: warning)
Faith that's Full of Hope, 10:32-39 (the road forward: encouragement)
Faith that's Genuine, 11:1-3 (what faith is)
Faith that's Godly, 11:4-40 (how faith behaves)
Faith that Perseveres, 12:1-29 (when faith endures)
II. AN OBSERVATION OF TODAY'S PARTICULARS
v4, Abel's sacrifice
v5, Enoch's walk
v6, (the pleasure of God)
v7, Noah's fear
v8, Abraham's call
v9, Abraham's sojourn
v10, Abraham's expectation
v11, Sarah's conception
she was past age, v11b
the way of women had ceased, Gen 18:11
Sarah laughed to herself, Gen 18:12-15 (Gen 18:9-10)
"She is my sister." Gen 20:2 (Gen 12:11)
considered Him faithful who had promised, v11c
God is faithful, Heb 6:13; 1Thess 5:24
She considered, Heb 10:29
received power to conceive, v11a
power, δύναμις (DOO-nam-is)
-- a. Luke 1:35
-- b. Acts 1:8
conceive, καταβολή (ka-ta-bo-LĀ)
-- a. "foundation"
-- b. 1 Pet 1:18-20
-- c. Eph 1:4-5
Genesis 21 has an unusually large number of interesting features embedded within the language of the text itself. What was Ishmael doing with or to Isaac that got Sarah so upset? Laughing at him, mocking him, or even molesting him? Why does this text say, "the angel of God" and not "the angel of Yahweh" as in ch. 16? We can learn much from the actual language used in this text.
But we can also learn a great deal about this biblical account specifically and the entire biblical meta-narrative by examining how Paul uses this chapter in his letters, especially in Galatians 4:21-31. Why can Paul take this passage as an allegory, when the Reformed hermeneutic discourages allegorical interpretation?
We can learn a great deal about God and His Word through passages like this one.
In Genesis 20, we see Abraham try to pass off his wife (and half-sister) Sarah as his mere sister, and this for a second time. But God intervenes to continue to protect the line that will produce the seed of the woman, this long-awaited son Isaac, both long-awaited by Sarah and Abraham, but also the next in line of that seed who would ultimately culminate in Jesus Christ, who would crush the head of the seed of the serpent.
But we also learn a few other things about God in His relations to mankind.
We learn that God can (and absolutely does) override the will of man. This is true even when it comes to salvation.
We also learn that God may strike a person ill to keep them from sinning further against Him.
These two massive truths are understood especially in the context of how we pray for people, and they should inform how we pray for both believers and unbelievers alike.