Gen 21: Birth of Sarah's son Isaac, Hagar and Ishmael mistreated and sent away, Abraham's and Abimelech's treaty

Isaac, the promised child, was born to Sarah and Abraham. Possibly due to jealousy, Ishmael was mocking of Isaac and as a consequence, he and his mother were sent away. "These things may be taken figuratively, for the women represent two covenants" (Gal 4:24)

• v1-2: God did as He had promised. Abraham was a hundred years old when he had Isaac. Sarah's womb was as good as dead, but the Word of God spoke life into being and a miracle occurred.
• v3-4: Abraham remained obedient to God and named his son as God directed.
• v6: Bearing a son filled Sarah with joy, and she acknowledged that it was only by God's grace and provision that she was able to conceive. Others would also laugh and rejoice in this instance of God's power and goodness, and be encouraged to trust in Him
• v7: Sarah was filled with wonder at the miracle that God had bestowed upon her, because God had been "able to do immeasurably more than all we ask or imagine, according to his power that is at work within us"(Eph 3:20)
• v8: The promised child grew; likewise as we are born again of the spirit must grow and increase of God.
• v9: Ishmael, fourteen years older than Isaac, mocked him. "At that time the son born in the ordinary way persecuted the son born by the power of the Spirit. It is the same now" (Gal 4:29). It is a warning that those who will live godly lives will be persecuted and mocked.
• v10: Notice that Sarah would have allowed Ishmael and Hagar to stay if Ishmael had not caused a disturbance and grief to Sarah. Likewise, none are rejected and cast out from God but those who have first deserved it.
• "Get rid of that slave woman" - it is quoted in gal 4:30 as if it had been spoken by a spirit of prophecy, even though it seems to have been spoken in a moment of anger. Paul describes it as the sentence passed on those born after the flesh and not born again i.e. those who reject the gospel promise. This was particularly referring to the rejection of the unbelieving Jews, who although were Abraham's seed, did not submit to the new covenant, choosing instead to mock and persecute the church.
• v11: Abraham was torn and grieved that Ishmael had given such a provocation.
• v12: God told Abraham what His will was. When in doubt, seek God! (: God set the matter before Abraham, and explained that the casting out of Ishmael was necessary to the establishment of Isaac in the covenant, because Isaac the promised son must be the father of the promised seed, through whom Christ and the church must descend (as Paul explains in Rom 9)
• v13: One cannot say that God was favouring one child over the other. He blessed Ishmael, and by promising to make him a great nation too, hence implied that His Hand would cover and protect Ishmael. The only reason that covenant blessings were to be given to Isaac alone was because God in His divine purpose needed it to be so to pave the way for the Messiah.
• v14: Abraham was swift to obey and act.
• v15-16: Ishmael and Hagar, away from the promise, were reduced to great distress as they wandered in the wilderness.
• v17-18: God appeared in the midst of distress, and sent an angel to comfort her. The angel assured her that God hears, and hence called her to lift up her son. No matter how far we wander into the wilderness, God hears our cry, and this knowledge of God's readiness to help us must quicken our endeavours to get up and keep going.
• v19: God opened Hagar's eyes, and she saw a well of water. Are you going to allow God to open your eyes to see His provision and His wells of grace?
• v20: God's presence never left Ishmael
• v21: Ishmael settled in the desert, and took up the wilderness of the world.

Abraham and Abimelech made a treaty.

• v22: Abimelech proposed the treaty, and was induced to it because he observed God's favour to Abraham
  "Give me a sign of your goodness,
  that my enemies may see it and be put to shame,
  for you, O LORD, have helped me and comforted me." (Ps 86:17)
• v24: Abraham consented to the treaty, and did not shy away from giving assurances
• v25: "If your brother sins against you, go and show him his fault, just between the two of you. If he listens to you, you have won your brother over" (Matt 18:15). Abraham chose to settle a matter of dispute at that moment.
• v27-31: Abraham gave a generous gift to Abimelech in token of friendship, and ratified the covenant by an oath, so that they might always remember it.
• v33: Even though Abraham was an alien in the land, he professed his religion openly, calling on the name of the Lord in the grove he planted.