The Established Path of Discipleship

(An exposition of Genesis 21)

As we mature, we naturally become more introspective. We find ourselves pausing to reflect on our lives, attempting to decipher the meaning behind our experiences. We recall our failures, our triumphs, our struggles, and our blessings. But what does it all signify? It’s a challenge, isn’t it, to comprehend God’s actions when we’re in the midst of them? They say hindsight is 20/20, or rather, God-centered hindsight is 20/20.

I suppose our father Abraham did a little bit of reflecting, too. As he reflected on his 100 years of life, I think he tried to make some sense of all the twists and turns in his walk of faith. He certainly had his share of successes, failures, trials, and blessings. All of this comes to a head when God fulfills his promise of a son, Isaac. God shows us through this Scripture that he is an everlasting God who makes and keeps eternal promises.

God fulfills his promise precisely (vv. 1-7).

When God makes a promise, he fulfills his promise with exact precision. Look closely at verses 1-2,

The LORD visited Sarah as he had said, and the LORD did to Sarah as he had promised. And Sarah conceived and bore Abraham a son in his old age at the time of which God had spoken to him.

The text underscores the precision of God in these two verses. How did the LORD visit Sarah? The answer is precisely as he had said. What did the LORD do to Sarah? Again, exactly as he had promised. When did Sarah conceive? At the precise time God had spoken to Abraham. Do you see the perfection here? Do you see the precision here? God had promised Abraham in Gen. 18:9, “At the appointed time I will return to you, about this time next year, and Sarah shall have a son.” God fulfilled this promise with absolute precision to the day.

 Isn’t this what we celebrate at Advent/Christmas time? We celebrate God’s precision in fulfilling his promise. Galatians 4:4, “But when the fullness of time had come, God sent forth his son, born of woman, born under the law.” Let me remind you of God’s precision in fulfilling this promise of a Savior:

Promise	Fulfillment
Born of a woman (Gen. 3:15)	Matt. 1:20, Gal. 4:4
Born in Bethlehem (Mic. 5:2)	Matt. 2:1, Luke 2:4-6
Born of a virgin (Is. 7:14)	Matt. 1:22-23, Luke 1:26-31
Come from the line of Abraham (Gen. 12:3, 22:18)	Matt. 1:1, Rom. 9:5
Descendant of Isaac (Gen. 17:19, 21:12)	Luke 3:34
Descendant of Jacob (Num. 24:17)	Matt. 1:2
Tribe of Judah (Gen. 49:10)	Luke 3:33, Heb. 7:14
Heir to King David’s throne (2 Sam. 7:12-13, Is. 9:7)	Luke 1:32-33, Rom. 1:3
Called Immanuel (Is. 7:14)	Matt. 1:23

This kind of precision is meant to strengthen your faith. It is intended to increase your confidence not in yourself but in the God who acts with perfect precision to save and redeem you.

God fulfills his promise profoundly (vv. 8-21).

 Abraham holds a big feast when Isaac is two or three years old. Instead of rejoicing over the birth of his brother, Ishmael laughs mockingly at the toddler. Sarah sees this and is displeased. So she says to Abraham, “Cast out this slave woman with her son, for the son of this slave woman shall not be heir with my son Isaac.” What should have been a day of rejoicing for Abraham turns sorrowful, according to verse 11. God tells Abraham not to be displeased but to do as Sarah told him. God reassures Abraham that he will make Ishmael into a nation. So Abraham sends them away the following day and gives them as many provisions as possible.

 I can only imagine what Abraham must have been feeling and thinking. This was his son Ishmael, whom he loved. How can sending your son away into the desert with meager provisions be good? It’s at times like these when we wonder what God is doing. God, how can this be your will? This is what I mean by God fulfilling his promise profoundly. It is profound in that it is deep and mysterious. Romans 11:33, “Oh, the depth of the riches and wisdom and knowledge of God! How unsearchable are his judgments and how inscrutable his ways!” Scripture does shed more light on this passage in Galatians 4:28-31:

Now you, brothers, like Isaac, are children of promise. But just as at that time he who was born according to the flesh persecuted him who was born according to the Spirit, so also it is now. But what does the Scripture say? “Cast out the slave woman and her son, for the son of the slave woman shall not inherit with the son of the free woman.” So, brothers, we are not children of the slave but of the free woman.

As followers of Christ, we are children of promise. Just as Ishmael (the one born according to the flesh) persecuted Isaac (the one born according to the Spirit), so we who know Christ (we are born of the Spirit) are persecuted by the people in the world (ones born according to the flesh). This Old Testament passage paints a picture of what was to come.

You and I can take comfort in this passage by knowing that just as God was shaping and molding Abraham and profoundly fulfilling his promise, God is doing the same in our lives. Sometimes, it is profound, deep, and beyond our knowing, but we can be assured that God is molding us into his glory. He will fulfill his promise, even though it seems mysterious to us.

God fulfills his promise perpetually (vv. 22-34).

Our God is a God of infinite grace. Remember what a lousy witness Abraham was in chapter 20? Remember how he showed a lack of faith and confidence in God before Abimelech by saying Sarah was his sister? But notice how God is working in Abraham’s life. God slowly and methodically shapes Abraham, and in chapter 21, he restores Abraham’s witness. Abimelech is rebuking Abraham in chapter 20; now, Abimelech is praising Abraham in verse 22, “God is with you in all that you do.” Because of this, Abraham can make a covenant with Abimelech to settle a dispute over a well. Sometimes, we think God will never use us after a significant fall, but Abraham’s experience encourages us.

 Abraham plants a tamarisk tree and calls on the name of the Lord, the Everlasting God. Little details like this in the text can easily escape our notice, but they are essential. Why plant a tamarisk tree? Why this addition of the name the Everlasting God? The tamarisk tree symbolized fruitfulness in Middle Eastern culture in Abraham’s day. God had so shaped and molded Abraham throughout his life that Abraham was now a fruitful witness for the Lord. God is called the Everlasting God here to highlight the eternal and perpetual nature of his promise to Abraham.

You can trace the fulfillment of God’s promise to Abraham throughout the Old Testament and into the New Testament fulfillment in Christ. You can also see this promise being fulfilled every day. Every time someone comes to faith in Christ, God is fulfilling his promise to bless the nations through the seed of Abraham. Every time a child of promise is born, we are reminded of the Everlasting God. As we read our Bibles from Genesis to Revelation, we see God will fulfill this promise into eternity as we dwell with him as his people in the New Jerusalem—not the one of the earth—but the one of heaven.

Conclusion

You may not be as old as me, but I want you to do something. Please do some reflecting today. I want you to think about how precise God was in bringing you to Christ—calling you to himself. Think about everything God did to bring you to Christ. I want you to look back and see God’s hand in the times in your life when you could not figure out what God was doing. Look now and reflect on how God was working profoundly and mysteriously. He was molding you and shaping you into who you are today. He was making you more and more like Jesus.  Think about how eternal is his promise—the fact that he will do as he has said, as he has promised, and at the appointed time. Reflect, think, and be encouraged. He is an everlasting God who makes and keeps his eternal promise.