This was disputed in previous comments, so I will give Jesus’s prophecy: “Verily I say unto you, This generation shall not pass, till all these things be fulfilled.” (Matthew 24:34) Here is that verse in context, explaining what was to be fulfilled while the generation listening to Jesus was alive: 29 Immediately after the tribulation of those days shall the sun be darkened, and the moon shall not give her light, and the stars shall fall from heaven, and the powers of the heavens shall be shaken: 30 And then shall appear the sign of the Son of man in heaven: and then shall all the tribes of the earth mourn, and they shall see the Son of man coming in the clouds of heaven with power and great glory. 31 And he shall send his angels with a great sound of a trumpet, and they shall gather together his elect from the four winds, from one end of heaven to the other. 32 Now learn a parable of the fig tree; When his branch is yet tender, and putteth forth leaves, ye know that summer is nigh: 33 So likewise ye, when ye shall see all these things, know that it is near, even at the doors. 34 Verily I say unto you, This generation shall not pass, till all these things be fulfilled. (Matthew 24:29-34)
Elsewhere Matthew makes it clear that “this generation” means the disciples standing before Jesus: “27 For the Son of man shall come in the glory of his Father with his angels; and then he shall reward every man according to his works. 28 Verily I say unto you, There be some standing here, which shall not taste of death, till they see the Son of man coming in his kingdom.” (Matthew 16:27-28)
Luke agrees:
“But I tell you of a truth, there be some standing here, which shall not taste of death, till they see the kingdom of God.” (Luke 9:27)
“Verily I say unto you, This generation shall not pass away, till all be fulfilled.” (Luke 21:32)
Mark agrees:
“Verily I say unto you, That there be some of them that stand here, which shall not taste of death, till they have seen the kingdom of God come with power.” (Mark 9:1)
“Verily I say unto you, that this generation shall not pass, till all these things be done.” (Mark 13:30)
Jesus told his accusers that they would see his return:
“And ye shall see the Son of man sitting on the right hand of power, and coming in the clouds of heaven.” (Mark 14:62)
Revelation’s author agreed because he said “the time is at hand” and that the horrors he predicted would “shortly come to pass” and that “every eye” of all people alive at the time — including those who pierced and murdered Jesus — would see him descend from the clouds. (Revelation 1:1-7, 22:10)
Nothing could be clearer, and it’s obvious the earliest Christians were expecting Jesus to return during their lifetimes, which is why Paul had to talk them down. And Paul echoed the claim that some Christians living at that time (“we”) would still be alive when Jesus returned. (1 Thessalonians 4:15, 1 Corinthians 15:51-52)
“Listen, I tell you a mystery: We will not all sleep [die] but we will all be changed.” (1 Corinthians 15:51-52)
To recap, the things to be fulfilled while the people of that generation were still alive included:
- The sun darkened.
- The moon no longer shining.
- Stars falling from the sky and the heavens shaken.
- Jesus appearing in the clouds with power and great glory, to be seen by all the people of the earth.
- The angels appearing with the great sound of a trumpet to gather the elect from every part of the earth.
