If you are here today and you are still in darkness, please look up - you will see the Light of Christ shining down pleading with you by the blood of Jesus to surrender your life to Him and receive His mercy through the forgiveness of your sins and then follow Christ.
Life can only be given to us by Christ! So, when we look at Hagar, she can not provide life, but in her son, who should not have been born, we see the sentence to sin, bondage and death. There was no inheritance in God for Ishmael.
Sarah, on the other hand, represents the Covenant of Promise or of Grace. Sarah represents grace, for it is only through Grace can anyone be saved and freed to live the life of Christ for all eternity. (Every Christian is born out of the grace of God through faith in Christ! (Ephesians 2:8-9, 8 “For it is by grace you have been saved, through faith—and this is not from yourselves, it is the gift of God— 9 not by works, so that no one can boast.”) Isaac was born through the Spirit and basically represents faith because of the faith of his father, which was born out the Promise of God.
There is now conflict between those who follow the covenant of the law and those who follow the covenant of grace. As seen in the events of the lives of Ishmael and Isaac, Ishmael persecutes his younger half brother and creates trouble in the family. So too does the children of the law, or those of the flesh, they seek to persecute and cause trouble for those who walk by the Spirit and who believe in Christ by faith alone.
In talking of these two women, Paul uses the physical Jerusalem as a representative of Hagar and says she represents all of her children as slaves to sin. But on the other hand, Sarah represents the New Jerusalem which is above that stands for freedom from sin. You can read the event (Genesis 21) where Abraham finally realizes that the slave handmaid, Hagar, and her son, Ishmael, his first born son, was not be able to continue to live with them but had to be driven out into the desert. The concept presented here is that slavery to sin can no longer be a part of the life of the saved person, who by the grace of God, now has eternal life here and then in eternity in heaven.
Please hear this. When the Bible tells of an event like this and you think that it is awful cruel of Abraham and God to do this to the woman and her son, you must not look at it from your point of view but from God’s. God was not only providing for the Son of Promise and his being raised as a Godly man but God was also telling the spiritual story of how slavery to sin and a righteous life can not live in the same life.
God’s love is the same for all men. Yet, He is sovereign and does as He desires. What we think is fair does not bare on the Father, Creator. There is one thing that we can tell you today, God has told us in His word, whosoever shall believe in Him will be saved. He has planned whereby all who are willing to faith in Jesus believed that died on the cross and was buried and then rose again from the dead, that person will be saved. He put it like this in Romans 10:9-13,