Genesis 21:5 · Bible study
Genesis 21:5 Commentary: God's Faithfulness at Abraham's Age 100
Hebrew · 6 what the commentators say
Meaning in one sentence
Why does the Bible note Abraham's age at Isaac's birth?
Research Summary
- Meaning: God's promise fulfilled exactly as said, against all natural odds, at the precise time He had appointed.
- Key words: 'one hundred years' (age as sign of impossibility), 'Isaac' (he laughs), 'born to him' (fulfillment of covenant).
- Main debate: None significant; all traditions read the verse as a historical and theological anchor for God's faithfulness.
- Theological theme: God's faithfulness and omnipotence in keeping covenant promises against human limitation.
- Best use: Preaching and teaching on faith, patience, and God's perfect timing; a model for waiting on God.
Translation Comparison
BSB Berean Standard Bible 2020
Abraham was a hundred years old when his son Isaac was born to him.
WEB World English Bible 2000
Abraham was one hundred years old when his son, Isaac, was born to him.
KJV King James Version 1769
And Abraham was an hundred years old, when his son Isaac was born unto him.
ASV American Standard Version 1901
And Abraham was a hundred years old, when his son Isaac was born unto him.
YLT Young's Literal Translation 1898
And Abraham is a son of a hundred years in Isaac his son being born to him,
Darby Darby Bible 1890
And Abraham was a hundred years old when his son Isaac was born to him.
Douay-Rheims Douay-Rheims Bible 1899
When he was a hundred years old: for at this age of his father, was Isaac born.
Translations in other languages (10 available)
Y era Abraham de cien años, cuando le nació Isaac su hijo.
E era Abraão de cem anos, quando lhe nasceu Isaque seu filho.
Abraham était âgé de cent ans, à la naissance d’ Isaac, son fils.
Hundert Jahre war Abraham alt, da ihm sein Sohn Isaak geboren ward.
En Abraham was honderd jaren oud, als hem Izak zijn zoon geboren werd.
Or Abrahamo aveva cento anni, quando gli nacque il suo figliuolo Isacco.
A było Abrahamowi sto lat, gdy mu się urodził Izaak, syn jego.
Авраам был ста лет, когда родился у него Исаак, сын его.
他兒子 以撒 生的時候，亞伯拉罕 年一百 歲。
Now Abraham was a hundred years old when the birth of Isaac took place.
Verse in Context
Original Language (Biblical Hebrew)
Old Testament · Biblical Hebrew · Genesis 21:5
Source: STEPBible TAGNT/TEHB (CC-BY 4.0). Click or tap a morphology code to see the full parsing.
Scholars' Consensus
Commentators across traditions agree that the precise notation of Abraham's age is meant to highlight the miraculous nature of Isaac's birth. Calvin argues that Moses records Abraham's age 'the better to excite the minds of his readers to a consideration of the miracle.' The Geneva Bible Notes similarly rest the weight on the age as a marker of divine intervention. Gill points out the chronological gap: Abraham was 75 when he left Haran, so the 100-year mark comes exactly 25 years later, matching the date of the promise in Genesis 17:1. Keil and Delitzsch describe Isaac as 'the fruit of omnipotent grace working against and above the forces of nature.' Matthew Henry ties the birth to the exact fulfillment of God's word: 'No word of God shall fall to the ground; for he is faithful that has promised.' The age thus signals not merely a human achievement but the convergence of divine timing and power.
How settled is the interpretation?
Interpretive difficulty: Low
What is clear: The verse plainly records the fulfillment of God's promise at the exact time and age He had declared, leaving no doubt about His faithfulness.
What Scholars Agree and Debate
| Topic | Agreed | Debated |
|---|---|---|
| Historicity of Abraham's age | All Christian traditions accept the literal age of 100 as historical and as part of the inspired record. | No substantive debate; the age is uniformly read as factual. |
| Nature of Isaac's birth | All traditions see the birth as a supernatural miracle, given Abraham's and Sarah's biological incapacity. | No substantive debate; the miracle is universally affirmed. |
| Theological significance of the age | The age demonstrates God's faithfulness, power, and the importance of trusting His word over human ability. | Some traditions (e.g., Matthew Henry) emphasize typology (Isaac as type of Christ). Others (e.g., Keil & Delitzsch) focus on the contrast between grace and nature. Both are complementary, not conflicting. |
Historical & Cultural Context
By the time of Isaac's birth, Abraham had waited twenty-five years since God first called him from Haran at age seventy-five (Genesis 12:4). When the promise of a son was renewed in Genesis 17, Abraham was ninety-nine and laughed at the thought of a child at age one hundred (17:17). Sarah herself was ninety, long past childbearing. The marriage had been fruitless for more than sixty years, as Calvin notes. This stark biological impossibility sets the stage for a deliberate miracle.
The location is likely Beersheba, where Abraham had settled (Gill cites Genesis 21:33). The name Isaac, meaning 'he laughs', permanently memorializes both Abraham's earlier laughter of incredulity (17:17) and Sarah's later laughter of joy (21:6). The circumcision on the eighth day (21:4) links Isaac to the covenant sign given in Genesis 17. The cross-reference in Romans 4:19 shows Paul reading this same age as emblematic of Abraham's faith: 'Without being weakened in faith, he didn't consider his own body, already having been worn out (he being about a hundred years old).' The verse thus functions as a historical anchor and a theological paradigm.
Textual Notes
The consulted sources note no significant textual variants for this verse. The Hebrew text is stable across manuscripts, and the verse appears without substantial differences in the Septuagint, Vulgate, and later translations. The reading is secure.
Reception History
From the early church onward, this verse has been read as a cornerstone of God's covenant faithfulness. Calvin used it to stimulate wonder at the miracle and to rebuke doubt. The Geneva Bible margin simply restates the age as a matter of fact. John Gill correlated the date with extra-biblical sources like Demetrius and Bishop Usher's chronology, demonstrating historical precision. Matthew Henry drew out the typology of Isaac as the long-awaited seed, prefiguring Christ. Keil and Delitzsch emphasized the theological depth: Isaac as fruit of omnipotent grace. In both Christian and Jewish tradition, the verse is part of the story of God keeping His word against all odds.
Preaching This Verse
Three-point outline
- God keeps His promises in His timing. The age 100 is not random; it is the exact year God had foretold (Gen 17:21). What seems late to us is precisely on schedule with God.
- God's power works where human ability ends. Abraham and Sarah were biologically incapable of having children. Their age magnifies the miracle and reminds us that God does not need our strength to fulfill His purposes.
- God's faithfulness is cause for joy. Sarah's laughter (21:6) transforms an old couple's doubt into public celebration. The birth of Isaac becomes a sign that God can turn our waiting into worship.
Five-point outline
- The promise given (Gen 17:16, 19), God singles out Isaac as the heir, establishing a covenant.
- The long wait, 25 years of silence, testing, and incremental revelation.
- The impossible situation, age, barrenness, and deadness of Sarah's womb (Rom 4:19).
- The exact fulfillment, at the set time, at age 100, God acts (Gen 21:2).
- The joyful response, Sarah's exclamation and Isaac's name serve as a perpetual reminder of God's grace.
Illustration hooks
- Waiting for a medical diagnosis: a long period of uncertainty that finally yields good news, reminding us that timing belongs to God.
- A prodigal child's return: years of prayer and silence, then one phone call that changes everything.
- A long-deferred career or calling: someone who has been faithful in obscurity for decades suddenly sees a door open.
Questions your congregation is asking
- Why does God make us wait so long for answers to prayer?
- How can I trust God when my circumstances say a promise is impossible?
- What does the specific age of Abraham tell me about the character of God?
Leading a Discussion
Genesis 21:5 may seem like a simple chronological note, but it carries the weight of twenty-five years of waiting and a lifetime of faith. This verse invites us to see God's hand in the details and to trust His timing even when hope seems lost.
Discussion questions
- What does Abraham's age at Isaac's birth reveal about the human situation?
- Read Genesis 17:1, 17:17. How does the context of the promise deepen your understanding of this verse?
- How does Paul use Abraham's age in Romans 4:19? What does that tell us about faith?
- Why do you think the Bible records such specific ages for key events?
- What does this verse teach about God's character and His relationship with His people?
- How can this encourage someone who is waiting for God to act in their life?
- What 'impossible' situations are you facing where you need to remember God's faithfulness at Abraham's age 100?
Word Study
The key original-language words in this verse. Select any word for its full lexicon entry — meaning, every occurrence in Scripture, and related words.
Cross-References
Source: Treasury of Scripture Knowledge (TSK, public domain)
| Genesis 17:1 | When Abram was ninety-nine years old, Yahweh appeared to Abram and said to him, “I am God Almighty. Walk before me and be blameless. |
| Genesis 17:17 | Then Abraham fell on his face, and laughed, and said in his heart, “Will a child be born to him who is one hundred years old? Will Sarah, who is ninety years old, give birth?” |
| Romans 4:19 | Without being weakened in faith, he didn’t consider his own body, already having been worn out, (he being about a hundred years old), and the deadness of Sarah’s womb. |
Interlinear and lexical data from STEPBible (CC BY 4.0). Cross-reference data from OpenBible.info (CC BY 4.0). Commentaries are public domain.
For personal reflection
Read the devotional page — prayer, application, and "for families"
What the Commentators Say
6 public-domain commentaries, condensed into plain language.
Calvin's Commentaries Reformed 1564
Calvin highlights that the miracle of Isaac's birth lies not in Abraham's natural ability but in God's power, since the marriage had been barren for over sixty years. He interprets Sarah's response as genuine joy and praise, not shame, so her "laughter" means others will rejoice with her.
Geneva Bible Notes Reformed 1599
The Geneva Note highlights Abraham's advanced age of one hundred years when Isaac was born. This detail underscores the miraculous fulfillment of God's promise, showing that nothing is impossible for the Lord to accomplish.
Gill's Exposition of the Bible Baptist 1748
Gill highlights that Isaac's birth came exactly twenty-five years after Abraham left Haran, when Abraham was one hundred. He notes that this precise timing, corroborated by an ancient historian, demonstrates both God
Keil & Delitzsch OT Commentary Protestant 1876
Keil-Delitzsch highlights that Isaac's name, meaning laughter, captures the contrast between God's promise and human inability. Abraham and Sarah's laughter first came from unbelief at the impossibility, but the miraculous birth transformed it into joyous amazement. Isaac is therefore the fruit of omnipotent grace working beyond natural forces.
Lange's Commentary Reformed 1857
Lange highlights how the shift to the divine name Elohim in this chapter reflects God’s general providence over those outside the specific covenant line, such as Hagar and Abimelech who do not yet know Jehovah. He argues that Sarah’s naming of Isaac connects directly back to Genesis 17, framing the child as a miraculous gift from God that brings joy and laughter to all who hear of his birth.
Matthew Henry's Commentary Reformed/Presbyterian 1710
Henry emphasizes that God's acts look brightest when measured against His own word: Isaac was born exactly when God had promised, proving no word from God fails. He also sees Isaac as a type of Christ, the long-promised seed that holy men had expected across the ages.