The below verses were addressed to the Jews who were THEN LIVING. Notice that Jesus was then speaking from Heaven–VERSE 25–where Heavenly Jerusalem (New Jerusalem) was after the destruction of Jerusalem in 70 AD and when this is written.
READ CAREFULLY BECAUSE HEAVEN AND EARTH DID PASS AWAY–70 AD (AS JESUS SAID WAS HAPPENING DURING THE GENERATION OF THE DISCIPLES). BELIEVING THAT THESE EVENTS DID NOT OCCUR DURING THE GENERATION OF THE DISCIPLES BUT BELIEVING THESE EVENTS ARE IN OUR FUTURE MEANS ONE IS NOT READING WHAT JESUS SAID TO HIS DISCIPLES AND THUS CANNOT BELIEVE IN THE HEAVENLY (NEW) JERUSALEM AND CANNOT UNDERSTAND THAT THE TEMPLE WAS DESTROYED IN 70 ADSO THAT THEKINGDOMCOULD BE ESTABLISHED ON EARTH INSIDE US—CHRIST IN YOU THE HOPE OF GLORY. COLOSSIANS 1:26-27. MANY PROPHETS AND RIGHTEOUS MENCANNOT SEE OR HEAR THEKINGDOM. MATTHEW 13:17.
22 But ye are come unto mount Zion, and unto the city of the living God, the heavenly Jerusalem, and to an innumerable company of angels,
23 To the general assembly and church of the firstborn, which are written in heaven, and to God the Judge of all, and to the spirits of just men made perfect,
24 And to Jesus the mediator of the new covenant, and to the blood of sprinkling, that speaketh better things than that of Abel.
25 See that ye refuse not him that speaketh. For if they escaped not who refused Him [Jesus] that spake on earth, much more shall not we escape, if we turn away from Him that speaketh fromheaven:
26 Whose voice then shook the earth: but now he hath promised, saying, Yet once more I shake not the earth only, but also heaven.
34 Verily I say unto you, This generation shall not pass, till all these things be fulfilled.
35 Heaven and earth shall pass away, but my words shall not pass away.
30 Verily I say unto you, that this generation shall not pass, till all these things be done.
31 Heaven and earth shall pass away: but my words shall not pass away.
32 Verily I say unto you, This generation shall not pass away, till all be fulfilled.
33 Heaven and earth shall pass away: but my words shall not pass away.
17 Think not that I am come to destroy the law, or the prophets: I am not come to destroy, but to fulfill.
18 For verily I say unto you, Till heaven and earth pass, one jot or one tittle shall in no wise pass from the law, till all be fulfilled.