His disciples asked Jesus to observe the beauty and structure of the temple and Jesus told them that not one stone would be left upon another that would not be thrown down. Rome sent in General Titus some 37 years later and he laid siege to and sacked Jerusalem and destroyed it and the temple so that there was not one stone left upon another that had not been thrown down. Now, Jesus was also talking about the signs of the times when He would return and how His followers would suffer in every generation.
A crucial sign is that the Gospel would be preached in all the nations not only a testimony against those who would not believe but to those who will hear the Gospel of Jesus Christ and believe. God has many people in every generation that will believe when they hear the words of life. Their names were written in the Lambs Book of Life before the foundation of the world.
Revelation 13:8 says in speaking about those who would worship the anti-Christ, “And all that dwell on the earth shall worship him, every one whose name hath not been written from the foundation of the world in the book of life of the Lamb that hath been slain.
But to those that refuse to believe, there are none who can say they never knew or heard. In Romans 1, the Apostle Paul says those who know there is a God but still live carnally have no excuse:
19 because that which is known of God is manifest in them; for God manifested it unto them.
20 For the invisible things of him since the creation of the world are clearly seen, being perceived through the things that are made, even his everlasting power and divinity; that they may be without excuse.
Now, we read in Mark what Jesus had to say about the signs of the times:
Mark 13:3-13
3 And as he sat on the mount of Olives over against the temple, Peter and James and John and Andrew asked him privately,
4 Tell us, when shall these things be? and what shall be the sign when these things are all about to be accomplished?
5 And Jesus began to say unto them, Take heed that no man lead you astray.
6 Many shall come in my name, saying, I am he; and shall lead many astray.
7 And when ye shall hear of wars and rumors of wars, be not troubled: these things must needs come to pass; but the end is not yet.
8 For nation shall rise against nation, and kingdom against kingdom; there shall be earthquakes in divers places; there shall be famines: these things are the beginning of travail.
9 But take ye heed to yourselves: for they shall deliver you up to councils; and in synagogues shall ye be beaten; and before governors and kings shall ye stand for my sake, for a testimony unto them.
10 And the gospel must first be preached unto all the nations.
11 And when they lead you to judgment, and deliver you up, be not anxious beforehand what ye shall speak: but whatsoever shall be given you in that hour, that speak ye; for it is not ye that speak, but the Holy Spirit.
12 And brother shall deliver up brother to death, and the father his child; and children shall rise up against parents, and cause them to be put to death.
13 And ye shall be hated of all men for my name’s sake: but he that endureth to the end, the same shall be saved.
And as Jesus was about to ascend back into heaven, He commanded them to go out into the whole world and proclaim the Gospel and baptize those who believe in the name of the Father and of the Son and of the Holy Spirit. These are those in every generation that hear the voice of Jesus in their hearts and believe and repent and take up their crosses of suffering and follow Him. Their baptism in water is symbolic of dying to the flesh and then rising again alive in the spirit and then proceed to put away the deeds of the flesh (the lust of the eyes, the flesh and the pride of life).
Matthew 28:16-20
16 But the eleven disciples went into Galilee, unto the mountain where Jesus had appointed them.
17 And when they saw him, they worshipped him; but some doubted.
18 And Jesus came to them and spake unto them, saying, All authority hath been given unto me in heaven and on earth.
19 Go ye therefore, and make disciples of all the nations, baptizing them into the name of the Father and of the Son and of the Holy Spirit:
20 teaching them to observe all things whatsoever I commanded you: and lo, I am with you always, even unto the end of the world.