How long is a generation in the Bible?
Scripture uses the word "generation" in more than one way, and the difference matters: sometimes it counts years from father to son, and sometimes it marks out a kind of people. Anyone asking for a fixed number has to reckon with both senses, because the commentators show that the Bible itself moves between them.
The Plain Sense: One Link From Father To Son
The most basic meaning is a stretch of ordinary human life. One writer defines it before setting it aside as too narrow for prophecy:
J. N. Darby"Generation" is habitually used in Scripture in a way other than for the period of human activity, or from the birth of a son to the birth of his son — the length of a man's active life.
That plain sense is not wrong; it is simply limited to certain contexts. Where a family line is being traced, the word carries no more than that:
William KellyBy the term "generation" in a genealogy (as Matthew 1), or where the context requires it (as Luke 1:50), a lifetime is no doubt meant: but where is it so used in the prophetic Scriptures — the Psalms and so on?
Reckoning It At Forty Years
When the length is actually calculated, the working figure used is forty years — the age at which a man was reckoned to father his first son. This comes up in working out how long Israel stayed in Egypt:
Morrish Bible DictionaryNow if we reckon that at that time a man had his first son when he was forty years of age, there would have been ten generations in four hundred years.
The same span shapes the wilderness years, where one whole generation was allowed to die out before the next entered the land. Israel's forty-year test is echoed in the Lord's own forty days of testing:
F. W. GrantIsrael had their forty years of trial in the wilderness, the Lord His forty days... Forty is the well-known symbol of probation in the fullest way.
The Four Generations Promised To Abraham
God told Abraham his descendants would return to Canaan in the fourth generation, and the four links can be named exactly:
Morrish Bible DictionaryA much shorter period is implied in Genesis 15:16, which says of Israel in Egypt that "they shall come back here in the fourth generation"; and if we turn to Exodus 6:16-20 we find exactly four generations, thus: Jacob's son Levi. Levi's son Kohath. Kohath's son Amram. Amram's son Moses.
Commentators differ over how to fit those four generations with the four hundred years also mentioned in the same passage; one treats the larger figure loosely:
J. N. DarbyThe two events occupy 400 years; the fourth generation would then be the stay in Egypt... only it is what we call round numbers.
A Generation Can Mean A Type Of People
Alongside the count of years runs a second use, where the word describes character rather than a date. A lexicon definition is cited to make the point:
The Bible TreasuryParkhurst, in his Lexicon, gives as a meaning of genea: "Men of like quality and disposition, though of neither one place nor age"; and this is amply borne out — "You, O LORD, will keep them; you will guard us from this generation forever" (Psalm 12:7). In this text "generation" is obviously not limited to the set of people at any one time upon the earth.
Why "This Generation Shall Not Pass" Breaks The Clock
This is where the question becomes urgent. If the Lord's words in Luke 21:32 meant a span of years, His prophecy would have expired long ago. The placement of the saying settles it:
William KellyThe Lord has given us the positive proof, by the way in which verse 32 stands here, that "this generation" cannot mean a mere chronological space of thirty or even one hundred years, for it is brought in after the running out of Gentile times and the coming of the Son of man with power and glory, events still unfulfilled.
Read that way, two generations are running side by side, and both end at the same moment:
F. B. HoleThe unbelieving generation will not pass until the second advent, nor indeed will the generation of those that seek the Lord.
How Far One Life Reaches
The measure has a personal edge. What a person is before God carries beyond his own lifetime, for good as well as for harm:
George C. WillisTo the fourth generation David's ways brought down blessing on his descendants... What an exceedingly solemn consideration this is for each of us, to remember that our walk, day by day, may affect our children for blessing or otherwise, for as much as three, or even four generations, or for a very much longer time.
Summary
- Count — In a genealogy the word means a lifetime, one link from a father's birth to his son's; reckoned in years, roughly forty, giving ten generations to four hundred years.
- Character — Scripture also uses "generation" for people of one moral stamp, "of neither one place nor age," as in Psalm 12:7.
- Clock — Where the two senses collide, context decides; the placement of Luke 21:32 after events still future rules out thirty or a hundred years.
- Continuity — So the Christ-rejecting generation and the generation of those who seek Him both run on until He comes.
- Consequence — Meanwhile the measure lands on you: your daily walk can bless or blight three or four generations after you.