Genesis 21 :1-21 “The Son of Promise “

As we come to Genesis 21 we shall find here a birth that we have been eagerly waiting for - Isaac the promised son of the covenant. 

His name means   “laughter”. And so it is. The birth of this boy brings new joy and laughter into the lives of this old couple. And it is by all accounts a miraculous birth.   All this   reminds us very much of the language of the time in which we find ourselves right now - the  Christmas season-the remembrance of the birth of Christ our Lord. The story of Isaac in a sense prefigures the birth of our Lord Jesus Christ, who was long awaited, and born under mysterious circumstances, and who has brought laughter into the lives of many that have trusted in Him for their salvation.  

Indeed, the prefigurement of Christ is found in every book of the OT. [1] 

And yet, while it is a happy story, we shall also find that there are dark shadows lurking  in the background. This portion of Scripture that begins with laughter (21:1-7) ends  with a painful separation (21:8-21). We will learn lessons from both.

1.     21:1-7 :  God is faithful

"The Lord did to Sarah as He had promised."   Allow me to begin with a brief comment on the length of time it took for God to fulfill his promise to Abraham and Sarah.  The promise of an offspring  was first  made  in Chapter 12  when God called  Abraham out of Ur of the Chaldees. At that time he was 75 (12:4) ,  and Sarah  was 65  years old.  It took 25 years to fulfill that promise (see 21:5)!  

How are we to understand this?  We remember that Abraham  (like Adam) was foolish to listen to his wife  when she suggested that he take  her servant Hagar and have  a son by proxy.  Ishmael (who shall occupy our thoughts  in the second half)  was born as a result.  He could of course not be the son of the promise. He was born as a result of  the scheming  of  Abraham and Sarah.   So, apart from this setback,  what reason could  we provide for this long waiting? 

The answer is simply, “we don’t know!” 

All we do  know is that God chose to work in a mysterious way His wonders to perform[2], as He so often does!  The mystery of Divine Sovereignty in the outworking of things is so well expressed in Isaiah  55:9 :  

"For as the heavens are higher than the earth, so are my ways higher than your ways, and my thoughts than your thoughts.” 

Whatever we may think, the birth of Isaac was in the end a sovereign act of God, and, from God’s perspective it happened just at the right time. In that sense his birth was like that   of Jesus, who is the ultimate seed or offspring of Abraham, and who in God’s providence was born at just the right time (Gal. 4:4 ESV In the fullness of time). In both cases the sons of promise were conceived despite human reason and ability, and through the supernatural activity of God.

There may be a number of people here today who have been waiting on God to fulfill what they believe is a divine promise from the Word of God to them. What shall we say to this? 

• Be absolutely clear that you do have a clear promise from the Bible, and not from your own fancies. 
• Remember also that a Bibles text taken out of context is a pretext. 

God nowhere promises you in the Bible that you will have children if you had none so far.   

God nowhere promises you in the Bible that you will recover from every illness  and that you will be happy, wealthy and healthy  all the days of your life.  

God does not even promise that all the children of every believer will be converted.  

But  God  does  promise  that  He will “supply every need [3]of yours according to his riches in glory in Christ Jesus.“ (Phil. 4:19) 

He promises that, for any true believer, all things will work together for the good. (Rom. 8:28).  

He has promised that nothing will separate us from His love in Jesus Christ (Rom. 8:31-39). 

He has promised us that He will give the Holy Spirit to those who ask Him (Lk. 11:13). 

He has promised us that if He has begun a good work in us he will complete it (Phil. 1:6).  

He has promised to come again, and to take us to be where He is (Jn. 14:1-3). 

So we can wait, standing on these promises of God, but the precise times of the fulfillment of His promises are not made known to us. By faith we believe and by faith we cling to the promises of God. God, our Father knows the best timing!

In this case God had given a specific promise to Abraham and Sarah  and He was  going to fulfil it. God is faithful. And now Sarah is happy… very happy (21: 6,7). The Lord has turned her reproach into a blessing, and  Abraham  makes it known in a very vivid way. He  names  their  son , ‘Isaac’ … He laughs! (21:3)  

The application of this truth is exciting. Whatever  God promises, He will do. He will keep His word. And so we must learn to  trust Him. All of us have our own challenges in trusting the Lord, but Genesis 21  has been recorded  that you may know  that  God can be trusted. If we do not believe that God is faithful, then it will be very difficult for us to pray meaningfully.   

C.H. Spurgeon often encouraged his congregation to study the promises of God and to pray  according to the  promises  of God.   Rehearse the promises of God. Meditate on them. Remember them, and trust God for the outcome.  And do not shrink back (Hebr.  10:35-39). At long last we will see what we have hoped for, just as is the case here in 21: 1-7. 

2.  God's  common Grace is kind  to all mankind - but  His love  for His chosen people   is without equal. (21:8-21) 

In this portion of Scripture we find the doctrine of election applied.   It begins with an old   conflict in Abraham’s family life.  As Isaac, the son of promise   is weaned, Abraham  makes a great feast  for him,  and  we find that  Hagar  the mother of Ismael  laughs – but  not in a happy way , but in derision (21:9). At this point Sarah insists that Hagar leaves. Conflict is looming between the son of promise and the son born according to a sinful decision. 

Paul makes a great deal of this  story in his letter to the Galatians 4:21-31   where he  tells us that the two boys, Isaac and Ishmael and their two mothers, Sarah and Hagar are allegories of two covenants. Sarah bore the son of promise, corresponding to freedom, living by grace. Hagar  bore the son  born according to the flesh, bearing children for slavery, living by law. The plain fact concerning them is that they cannot co-exist!

To put that into gospel language: The son of promise, Isaac corresponds to those living under the gospel. A gospel man or woman relies on   that which Jesus Christ has done for them. If you have trusted in the Lord Jesus Christ, and have been born again by a second miraculous birth, then you belong to the line of Isaac, the son of promise.  By contrast, Ismael, the son of the flesh, relies  on himself. He judges himself by  his own legal  standards of self-  righteousness. These two systems cannot co-exist, and so we  find  that  Hagar and Ishmael  must leave.  This is not ultimately just a family squabble.   It is about a profound  biblical truth, and in   Psalm 83: 4-6 we find  an outworking  of all this. Here the Psalmist  shows us that  the nations  which are related to Israel  are insanely  jealous of them and therefore they  conspire against Israel.  

The distinction between Isaac and Ishmael is much more profound than we are able to understand  at face value.  It is a theological issue, and it is revealed, as we have already  seen in Galatians  4:21 ff. 

There are  ultimately only two kingdoms in this world – and to these two kingdoms belong  either the  children born of the flesh  or  the  children born of the promise.    And in his letter to the Galatians  Paul was saying, don't be surprised if the synagogue (the sons of the flesh, the sons of the Sinaitic law and hence ultimately the sons of Ishmael)  is persecuting you. 

And ultimately we shall see that Ishmael persecuted Isaac.  

So  do not be surprised  if the unbelieving seed of Abraham is persecuting  true  Christians. That is Paul's argument and therefore  he  continues:  

"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." (Gal. 4:30,31)

SENT OUT…. BUT NOT WITHOUT MERCY !

Sarah has asked Abraham to  send  Hagar and Ishmael away, and clearly   this causes Abraham  to be distressed.  Abraham loved this boy deeply. In fact, when God came to Abraham to promise him the birth of Isaac, do you remember Abraham's response? Oh, that Ishmael might live before you. (17:18). 

God, in response is not unkind. He promises  Abraham  that He will care  for the boy and his mother, and to him are given promises (21:13,18). Here  God says to Abraham, “Because I love you, Abraham, I will make him a great nation. I will protect him.”

All this is of great significance and later in Romans  9,  Paul will use  this  story  again to  help us to understand   that not all descendants of Abraham  are  sons  of the promise :

… and not all are the children of Abraham because they are his (physical ) offspring, but  through Isaac shall your offspring be named!” (cf. Rom. 9:6ff)

God is  much more merciful  to Ishmael than Sarah. And so often we think we are more merciful  than God. But  the truth is that God is much kinder.  Hagar and  Ishmael are not left destitute  by any means . And this is true of all the  unregenerate people of the world today. God is  kind and gracious  to those that deny him and curse him and  ignore him.  This will  obviously have an end, when Jesus returns as the Judge making a final separation between the two kinds of people. 

But this text makes it clear that  there are only  two kinds of people in this world  - and so it is  There are those that   love and follow the true  God who has made the heavens and the earth, and there are those that follow their own thoughts and their man made gods.  The two are not compatible.    So, God had to separate them, just  as he had separated  Abraham and Lot,  so  that his heart would be uncompromised and wholly God's. If God was going to establish His seed, it was going to be through Isaac alone.

Yes, it breaks  Abraham’s heart, but God must break His heart  to build his faith. There are so many lessons in this, but  for the sake of the table set before us, I say  only this: 

When you come to the Lord  Jesus (the ultimate Son of Promise) and you receive His righteousness , in the place of your own old insufficient self - righteousness, you become a son of Isaac, the  son the promise. And you will leave your old  ways of sin behind you. You will make a decisive  break  with ungodliness and continue with Jesus.  Amen !

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[1] In Genesis, Jesus is the seed of the Woman.  In Exodus, He is the Passover Lamb. In Leviticus, He is the Priest, the Altar and the Lamb of Sacrifice. In Numbers, He is the pillar of cloud by day, and the pillar of fire by night. In Deuteronomy, Jesus is the Prophet like Moses.  In Joshua, Jesus is the captain of our salvation. In Judges, He is our Judge and Law-Giver.  In Ruth, He is our Kinsman and Redeemer. In 1 & 2 Samuel, He is our trusted  prophet. In Kings & Chronicles, He is our reigning King. In Ezra, He is the rebuilder of the broken-down walls of  our human lives.  In Nehemiah, Jesus is our Restorer. In Esther, He is our Advocate. In Job, Jesus is our Ever-Living Redeemer. In  the Psalms, He is our Shepherd. In Proverbs, He is our Wisdom. In Ecclesiastes, He is our hope of  the resurrection. In the Song of Songs, He is our loving Bridegroom. In Isaiah, Jesus is the suffering Servant. In Jeremiah , He is the righteous  who is wronged. In Lamentations, He is our weeping prophet. In Ezekiel, He is the one with the right to rule. In Daniel, Jesus is the fourth man in the fiery furnace. In Hosea, Jesus is the faithful husband.In Joel, He is the one who baptises with the Holy Spirit and with  fire. In Amos, He is the restorer of Justice. In Obadiah, He is mighty to save. In Jonah, He is  the Word of God to the nations. In Micah,  He  is the feet of one who brings good news. In Nahum, Jesus is our stronghold in the day of trouble.

In Habakkuk, He is God  our Saviour. In Zephaniah, He is the King of Israel. In Haggai, He is the signet ring.

In Zechariah, He is our humble King riding on a colt. In Malachi, Jesus is the son of righteousness.

[2]  God works in a mysterious way, his wonders to perform-a hymn by William Cowper (1731-1800)

[3] Note : needs … not wants .  David was  able to testify in Psalm 37:25 : “ I have been young and now I am old, yet I have not seen the righteous forsaken, or his children begging for bread.”