Here's a summarized exegesis on Jesus' use of the phrase "this generation"
by Pastor D. Curtis:
Let's start by examining the meaning of the word "generation." Generation, in our text, comes from the Greek word
genea, which means, by implication: "an age." In
Thayer's Greek-English Lexicon of the NT, we can see that the "
genea" me ans: "The whole multitude of men living at the same time." William F. Arndt and Wilber Gingrich (
A Greek-English Lexicon of the NT and Other Early Christian Literature) define "
genea" as: "basically, the sum total of those born at the same time, expanded to include all those living at a given time,
contemporaries." If you look at the way Jesus used the word "generation," I think it will be abundantly clear that it
always refers to His contemporaries, the Jewish people of His own period. Let's look at a few of the uses of "generation":
that upon you may fall the guilt of all the righteous blood shed on earth, from the blood of righteous Abel to the blood of Zechariah, the son of Berechiah, whom you murdered between the temple and the altar. 36 "Truly I say to you, all these things shall come upon this generation. (Matthew 23:35-36 NASB)
Jesus is in the temple speaking to the Jews, He says that all the judgement that He had spoken about would come upon them. I don't know of any commentator who understands this as referring to any other than the existing generation.
"For just as the lightning, when it flashes out of one part of the sky, shines to the other part of the sky, so will the Son of Man be in His day. 25 "But first He must suffer many things and be rejected by this generation. (Luke 17:24-25 NASB)
What generation did Christ suffer many things from, and what generation rejected Him? It is clear, He is speaking of His contemporaries. Look at how some of the translations deal with Mark 13:30:
New English Bible: "I tell you this: the present generation will live to see it all."
Today's English Version: "Remember this! All these things will happen before the people now living have all died."
Moffatt's Translation:"I tell you truly, the present generation will not pass away, till all this happens."
Weymouth's Translation: "I tell you in solemn truth that the present generation will certainly not pass away until all this has taken place."
These translations make it quite clear. The meaning of the word was that of the "present" generation in the time of Christ; not to a future generation thousands of years away.
So in etymology and usage, "generation" means: "those born at the same time, contemporaries."
How long is a generation? John Walvoord said, "A generation is normally from thirty to one hundred years." Now, he is the only one I know of who gives it that broad of a span. Most commentators see a generation as referring to a thirty to forty year time period. More important than that, what does the Bible say about the time of a generation? Let's look and see:
Therefore all the generations from Abraham to David are fourteen generations; and from David to the deportation to Babylon fourteen generations; and from the deportation to Babylon to the time of Christ fourteen generations. (Matthew 1:17 NASB)
In this genealogical table, we have data to estimate the length of a generation. It tells us that from the captivity in Babylon until Christ are fourteen generations. Now the date of the captivity, in the reign of Zedekiah, is said to be 586 B.C. From 586 B.C. until the birth of Christ would be about 586 years, which, divided by fourteen, makes the average length of a generation about 41 years.