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Commentary on Genesis 21 verses 1–8
Long-looked-for comes at last. The vision concerning the promised seed is for an appointed time, and now, at the end, it speaks, and does not lie; few under the Old Testament were brought into the world with such expectation as Isaac was, not for the sake of any great person eminence at which he was to arrive, but because he was to be, in this very thin, a type of Christ, that seed which the holy God had so long promised and holy men so long expected. In this account of the first days of Isaac we may observe,
I. The fulfilling of God's promise in the conception and birth of Isaac, Gen 21:1, Gen 21:2. Note, God's providences look best and brightest when they are compared with his word, and when we observe how God, in them all, acts as he has said, as he has spoken. 1. Isaac was born according to the promise. The Lord visited Sarah in mercy, as he had said. Note, No word of God shall fall to the ground; for he is faithful that has promised, and God's faithfulness is the stay and support of his people's faith. He was born at the set time of which God had spoken, Gen 21:2. Note, God is always punctual to his time; though his promised mercies come not at the time we set, they will certainly come at the time he sets, and that is the best time., 2. He was born by virtue of the promise: Sarah by faith received strength to conceive Heb 11:11. God therefore by promise gave that strength. It was not by the power of common providence, but by the power of a special promise, that Isaac was born. A sentence of death was, as it were, passed upon the second causes: Abraham was old, and Sarah old, and both as good as dead; and then the word of God took place. Note, True believers, by virtue of God's promises, are enabled to do that which is above the power of human nature, for by them they partake of a divine nature, Pe2 1:4.
II. Abraham's obedience to God's precept concerning Isaac.
1.He named him, as God commanded him, Gen 21:3. God directed him to a name for a memorial, Isaac, laughter; and Abraham, whose office it was, gave him that name, though he might have designed him some other name of a more pompous signification. Note, It is fit that the luxuriancy of human invention should always yield to the sovereignty and plainness of divine institution; yet there was good reason for the name, for, (1.) When Abraham received the promise of him he laughed for joy, Gen 17:17. Note, When the sun of comfort has risen upon the soul it is good to remember how welcome the dawning of the day was, and with what exultation we embraced the promise. (2.) When Sarah received the promise she laughed with distrust and diffidence. Note, When God gives us the mercies we began to despair of we ought to remember with sorrow and shame our sinful distrusts of God's power and promise, when we were in pursuit of them. (3.) Isaac was himself, afterwards, laughed at by Ishmael (Gen 21:9), and perhaps his name bade him expect it. Note, God's favourites are often the world's laughing-stocks. (4.) The promise which he was not only the son, but the heir of, was to be the joy of all the saints in all ages, and that which would fill their mouths with laughter.
2.He circumcised him, Gen 21:4. The covenant being established with him, the seal of the covenant was administered to him; and though a bloody ordinance, and he a darling, yet it must not be omitted, no, nor deferred beyond the eighth day. God had kept time in performing the promise, and therefore Abraham must keep time in obeying the precept.
III. The impressions which this mercy made upon Sarah.
1.It filled her with joy (Gen 21:6): "God has made me to laugh; he has given me both cause to rejoice and a heart to rejoice." Thus the mother of our Lord, Luk 1:46, Luk 1:47. Note, (1.) God bestows mercies upon his people to encourage their joy in his work and service; and, whatever is the matter of our joy, God must be acknowledged as the author of it, unless it be the laughter of the fool. (2.) When mercies have been long deferred they are the more welcome when they come. (3.) It adds to the comfort of any mercy to have our friends rejoice with us in it: All that hear will laugh with me; for laughing is catching. See Luk 1:58. Others would rejoice in this instance of God's power and goodness, and be encouraged to trust in him. See Psa 119:74.
2.It filled her with wonder, Gen 21:7. Observe here, (1.) What it was she thought so wonderful: That Sarah should give children suck, that she should, not only bear a child, but be so strong and hearty at the age as to give it suck. Note, Mothers, if they be able, ought to be nurses to their own children. Sarah was a person of quality, was aged; nursing might be thought prejudicial of herself, or to the child, or to both; she had choice of nurses, no doubt, in her own family: and yet she would do her duty in this matter; and her daughters the good wives are while they thus do well, Pe1 3:5, Pe1 3:6. See Lam 4:3. (2.) How she expressed her wonder: "Who would have said it? The thing was so highly improbable, so near to impossible, that if any one but God had said it we could not have believed it." Note, God's favours to his covenant-people are such as surpass both their own and others' thoughts and expectations. Who could imagine that God should do so much for those that deserve so little, nay, for those that deserve so ill? See Eph 3:20; Sa2 7:18, Sa2 7:19. Who would have said that God should send his Son to die for us, his Spirit to sanctify us, his angels to attend us? Who would have said that such great sins should be pardoned, such mean services accepted, and such worthless worms taken into covenant and communion with the great and holy God?
IV. A short account of Isaac's infancy: The child grew, Gen 21:8. Special notice is taken of this, though a thing of course, to intimate that the children of the promise are growing children. See Luk 1:80; Luk 2:40. Those that are born of God shall increase of God, Col 2:19. He grew so as not always to need milk, but was able to bear strong meat, and then he was weaned. See Heb 5:13, Heb 5:14. And then it was that Abraham made a great feast for his friends and neighbours, in thankfulness to God for his mercy to him. He made this feast, not on the day that Isaac was born, that would have been too great a disturbance to Sarah; nor on the day that he was circumcised, that would have been too great a diversion from the ordinance; but on the day that he was weaned, because God's blessing upon the nursing of children, and the preservation of them throughout the perils of the infant age, are signal instances of the care and tenderness of the divine providence, which ought to be acknowledged, to its praise. See Psa 22:9, Psa 22:10; Hos 11:1.
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SUMMARY
Genesis 21:5 precisely records the age of Abraham—one hundred years—at the birth of his son, Isaac. This concise statement encapsulates the culmination of decades of divine promise and human expectation, powerfully underscoring the miraculous nature of Isaac's arrival and the unwavering faithfulness of God to His long-standing covenant pledges, bringing forth life beyond natural human capacity.
CONTEXT
Literary Context: Genesis 21:5 is situated at a pivotal juncture in the patriarchal narratives, immediately following the fulfillment of God's promise regarding Isaac's birth (Genesis 21:1-3) and preceding Sarah's joyful exclamation and the subsequent events involving Hagar and Ishmael. The preceding chapters, particularly Genesis 17 and Genesis 18, detail God's repeated assurances to Abraham that he would have a son through Sarah, despite their advanced age. This verse serves as the definitive chronological marker of this long-awaited event, solidifying the miraculous nature of Isaac's conception and birth, which was foretold to occur "at the set time next year" (Genesis 18:10). It is a direct and unambiguous declaration of the promise's realization, setting the stage for the unfolding of God's covenant plan through this specific lineage.
Historical & Cultural Context: In the ancient Near East, the ability to produce heirs, especially a male heir, was paramount for a family's legacy, social standing, and economic security. Barrenness was often considered a great misfortune or even a curse, bringing shame upon a woman and her husband. Abraham and Sarah, as a childless couple well past their reproductive years (Abraham was 99 and Sarah around 90 when the promise was reiterated in Genesis 17:17), faced immense cultural pressure and personal despair. Their situation made the prospect of a natural birth utterly impossible. Therefore, the explicit mention of Abraham's age in Genesis 21:5 is not merely a historical detail but a profound theological statement. It highlights that Isaac's birth was not a natural occurrence but a supernatural act of God, defying all biological and cultural expectations, thereby emphasizing God's unique power and faithfulness to His word.
Key Themes: This verse powerfully contributes to several overarching themes within Genesis and the broader biblical narrative. Foremost is the theme of Divine Faithfulness and Promise-Keeping, as God fulfills His word despite human impossibility and long delays. It underscores God's Sovereignty Over Nature, demonstrating His ability to transcend natural limitations and bring forth life where it is biologically impossible, asserting His control over creation and human biology. The birth of Isaac at this specific juncture also significantly advances the theme of Covenant Fulfillment, establishing the promised lineage through which the Abrahamic covenant would continue and ultimately bless "all the families of the earth" (Genesis 12:3). Furthermore, it introduces the theme of Laughter (the meaning of Isaac's name) as a response to God's work—initially of disbelief (Genesis 18:12), then of profound joy and wonder (Genesis 21:6).
EXPOSITION AND ANALYSIS
The concise statement of Genesis 21:5, "And Abraham was an hundred years old, when his son Isaac was born unto him," is pregnant with theological significance, marking the precise and miraculous fulfillment of God's long-standing promise.
Key Word Analysis
Verse Breakdown
Literary Devices
The primary literary device at play in Genesis 21:5 is Emphasis, particularly through the precise numerical detail of Abraham's age. By stating "an hundred years old," the text draws immediate and profound attention to the miraculous nature of the birth, leaving no room for doubt that this was a divine act, not a natural occurrence. This numerical emphasis serves to magnify God's power and faithfulness. Additionally, the verse employs Symbolism through the name "Isaac" (meaning "laughter"). This name is a symbolic encapsulation of the human response to God's seemingly impossible promise—initially disbelief and amusement, later transformed into profound joy and wonder. The very name becomes a perpetual reminder of the journey from human skepticism to divine fulfillment. The verse also functions as a powerful moment of Fulfillment, signaling the culmination of a long narrative arc of divine promise and human waiting, thereby reinforcing the theme of God's unwavering commitment to His word.
THEOLOGICAL AND THEMATIC CONNECTIONS
Genesis 21:5 stands as a monumental testament to God's absolute faithfulness and His sovereign power over all creation, including the very processes of life. It demonstrates that God's promises are not bound by human limitations or natural laws, but are fulfilled precisely according to His divine will and perfect timing. Isaac's birth, occurring when Abraham was a century old and Sarah was well past childbearing age, unequivocally asserts God's ability to bring life from what is naturally dead or barren. This event serves as a foundational biblical narrative affirming that what is impossible for humans is entirely possible for God, instilling profound hope and encouraging unwavering trust in His word.
REFLECTION AND APPLICATION
Genesis 21:5 offers profound and enduring encouragement for believers today, reminding us that the God of Abraham is still at work, faithful to His word, even when circumstances seem utterly impossible or the wait is long and arduous. Our human limitations and the apparent unlikelihood of a situation do not, in any way, limit God's power or His capacity to fulfill His promises. This verse calls us to cultivate a deep trust in God's perfect timing, believing that His plans unfold according to His divine schedule, not necessarily ours. It inspires us to persevere in faith in the face of seemingly insurmountable obstacles, knowing that what is impossible for us is entirely possible for God. Furthermore, the joy associated with Isaac's name points to the profound delight and wonder that accompanies the realization of God's promises in our lives, urging us to embrace that joy and give Him glory when His faithfulness is revealed. It compels us to ask ourselves where we are placing limits on God and to instead expand our vision to His limitless power.
Questions for Reflection
FAQ
Why is Abraham's age so emphasized in Genesis 21:5?
Answer: Abraham's age of one hundred years is emphasized in Genesis 21:5 to highlight the miraculous nature of Isaac's birth. It serves as a clear indicator that this was not a natural event but a direct, supernatural act of God. Both Abraham and Sarah were well past childbearing age, making a natural conception biologically impossible. This emphasis underscores God's omnipotence and unwavering faithfulness in fulfilling His promise despite all human limitations, ensuring that the credit for Isaac's existence belongs entirely to Him.
How does Isaac's birth relate to the Abrahamic covenant?
Answer: Isaac's birth is a pivotal moment in the fulfillment of the Abrahamic covenant, which God had established with Abraham in Genesis 12 and reiterated multiple times. God had promised Abraham countless descendants and that through his seed, all nations would be blessed. Isaac was the specific, promised heir (the "seed" mentioned in Genesis 17:19) through whom this covenant lineage would continue. His birth, therefore, was not just a family event but a foundational step in God's grand redemptive plan for humanity, establishing the line that would eventually lead to Christ.
What is the significance of Isaac's name, "laughter"?
Answer: The name Isaac (Hebrew: Yitschâq) means "he laughs" or "laughter," and its significance is multi-layered. It commemorates both Sarah's initial laughter of disbelief when she heard she would conceive in her old age (Genesis 18:12), and her subsequent laughter of profound joy and wonder upon his birth (Genesis 21:6). The name thus encapsulates the journey from human skepticism and doubt to divine faithfulness and overwhelming joy, serving as a perpetual reminder that God's promises, though seemingly impossible, bring forth ultimate delight when fulfilled.
CHRIST-CENTERED FULFILLMENT
The miraculous birth of Isaac to Abraham and Sarah in their old age, highlighted in Genesis 21:5, serves as a profound and multifaceted foreshadowing of the ultimate Son of Promise, Jesus Christ. Just as Isaac was conceived and born through divine intervention beyond natural human capacity, Jesus Christ was conceived by the Holy Spirit and born of the virgin Mary, transcending all biological limitations (Luke 1:34-35). Isaac was the "son of promise" through whom the covenant lineage and the blessing of Abraham would continue; similarly, Jesus is the ultimate "seed" of Abraham through whom the promise of salvation and blessing extends to all nations (Galatians 3:16). The seemingly impossible birth of Isaac demonstrated God's power to bring life from a "dead" womb (Romans 4:19), foreshadowing Christ's resurrection from the dead, which likewise demonstrated God's power to bring spiritual life to those who are spiritually dead (Ephesians 2:4-5). Thus, Isaac's birth is not merely a historical event but a foundational type, pointing forward to the greater, supernatural work of God in Christ, making possible not just a physical lineage, but spiritual reconciliation and eternal life for all who believe (John 3:16).