The parallels are found at Matthew 24:29-35 and Luke 21:25-33
In verses 5-13 Jesus gives us a survey of all time from when he was speaking (Tuesday of Holy Week) till the end of the world; in verses 14-23 He speaks of the destruction of Jerusalem and the overthrow of the Jewish nation; in verses 24-37 He speaks of His parousia and the very end of the world.
Concerning verses 24-31: Nestle Greek text makes this two paragraphs, the signs of the very end and the Parousia; 28-31, the admonitory lesson from the fig tree. Ylvisaker makes three paragraphs: 24-25, premonitions in nature; 26-27 the signs which shall attend the Lord's advent; 28-31, the time for the end. Beck makes verses 21-31 one section, entitled "Jesus is Come," with subparagraphs at 24, 28 and 30. That is worth studying. Very likely the false christs, false prophets, deceiving miracles and wonders refer to the end of the world, not the destruction of Jerusalem.
"But" dissociates the destruction of Jerusalem from the end of the world. The disciples and the original readers of Mark could not have identified the destruction of Jerusalem and the end of the world because of what is said in verse 10 and verses 32-37. The destruction of Jerusalem, of course, was a reminder of the end of the world. "Day" in verse 19 is contrasted to this verse where "day" must have a much wider meaning because we are here dealing with the very end of the world.
Ylvisaker: Jesus here speaks of the immediate premonitions in nature. Nature, both in heaven and on earth, shall pass through such an organic change that is must be obvious to everyone that the end is at hand. The forces of nature shall be transformed so thoroughly that it will be plainly apparent that the old order of things is in the process of dissolution.
Lenski: All that holds the heavenly bodies in their orbits and enables sun, moon, and stars to light the earth, shall give way. Thus the sun's light will be extinguished, the moon's radiance will disappear in the same instant, and the stars will come tumbling from their places.
Kretzmann: Then there will be signs such as are entirely out of the usual course of events in nature; no ordinary eclipses which follow laws and rules framed by God, but a return to chaos . . . There will be a great concussion of the powers of the heavens. The entire universe will go out of joint. The hand of God's providence and government will be withdrawn, and will be dissolved into its component parts.
Until then God has promised in Genesis 8:22: "As long as the earth stands, sowing and harvesting, cold and heat, summer and winter, day and night will not stop." (Beck's translation). Read Luke 17:22 for a comparison between the flood and the end of the world. The unbeliever scoffs at this, just as evolutionists scoff at the doctrine of creation. But Mark 13:31a, a restatement of verses 24-25, is a warning to the unbeliever and a comfort to the believer. By the way, verses 24-25 and their parallels rule out any and all ideas of the millenium.
Lenski: Here and in verse 27 'at that time' merely denotes succession, but almost instantaneous succession.
Beck: "Then people will see the Son of Man." By the way, this verse clearly speaks of the same incident as Daniel 7:13-14. This verse clearly says that the human nature of Christ will fully and brilliantly use all the power and glory of the divine nature. All will see Him thus. The adjective "all" goes with both nouns. "In clouds" is to be taken literally. This verse is a great comfort to the believer and a warning to the unbeliever.
"His" angels and "His" elect. It should go without saying that election will not take place then but only the gathering of the elect, both living and dead. Look at 1 Thessalonians 4:15-16. This verse rules out the millenium and the mass conversion of the Jews. Beck paraphrases the last part of the verse well: "From the north, south, east and west, and from one end of the world to the other." A very comforting passage.
The two conditional relative clauses introduced by "whenever" are clearly present general: "Whenever the branch . . . you always realize." "Whenever you see these things happening . . . always realize." Each spring when these things happen, people always realize that summer is near. Each time when Christians see signs, they always must realize that the end is near. He is not speaking of one spring and a few signs. He is speaking of something which is constant in life. The grammars and commentaries fail to point this out.
To interpret this verse of the Jews only, the conversion of the Jews, is absurd. The fig-tree was very common in Palestine. It is purely an illustration of spring. Luke, who adds: "and of all the trees" is writing for a larger audience, including Gentiles. The idea is precisely the same.
Point of comparison: clear signs alert us as to what is coming. It is implied here, and clearly stated in Luke, that the signs are so clear that no one need tell us what they mean, because they are constantly happening. Even a child understands that. Jesus credits the reader with the intelligence to know that "these things" refers to any and all signs in nature, politics, the family, society and even in the church. Signs are all those things over which we have no control: wars, rumors of war, controversies, inflation, the weather, troubles in families, death, eclipses, etc. The Christian is constantly being reminded by "all." The meaning is plain, He is near, the end is near, He is right at the door.
"I tell you the truth," always used in the Gospels of a solemn noteworthy assertion, plainly indicating Jesus' divinity. Note the very strong expression meaning: "Most certainly not." "Generation" denotes a certain kind not a span of time. Beck: "These people will not pass away till all this happens." NEB is surely wrong: "The present generation will live to see it."
Ylvisaker: Forced constructions are unnecessary if we accept the word in its literal sense, the generation of the Jews, the Jewish nation.
Lenski: This type of Jews will continue to the very Parousia. It has not ' passed away' to this very day. The voice of Jewish rejection of Jesus as the Christ is as loud and vicious as ever: 'He is not the Messiah, not the Son of God!' Here, therefore, is Jesus' own answer to those who expect a final national conversion of the Jews either with or without the fiction of a millenium.
Kretzmann: This people, the nation that had rejected Him, should not cease to be a distinct race of people, separate from all the rest, until Christ's coming in glory would take place. They should remain as a standing testimony and proof of the truthfulness of Christ's words.
Hendriksen: The expression 'all this' covers the events predicted for the entire dispensation, including even the final tribulation and the Lord's glorious return.
This verse tells us
For the former read 2 Peter 3:10-13; Romans 8:18-23; 1 Corinthians 7:31 and Revelation 21:1-5. Both annihilation and transformation of heaven and earth, as we now know it, are taught in Scripture. For the latter read 1 Peter 1:25 and Isaiah 40:8.
From this passage is taken the motto of Concordia Publishing House: Verbum Dei Manet in Aeternum. The Word of Jesus, of course, are not only those recorded here but all of Scripture.