“Lift up your eyes to the heavens, and look at the earth beneath; for the heavens vanish like smoke, the earth will wear out like a garment, and they who dwell in it will die in like manner; but my salvation will be forever, and my righteousness will never be dismayed.” Isaiah 51:6
The people of the New Testament had little problem imagining Jesus’ second coming at the end of the world. They had been personal witnesses of Jesus’ first coming and had heard Jesus talk about and his second coming.
In the last days before Jesus went to the cross to die for our sins he spoke at length about his second coming. He talked about the signs of his coming, signs in the heavens and on the earth, the persecution and trouble his followers would endure.
He talked about how he would appear in great glory with his angels and everyone would be assembled before him on his throne for Judgment Day. He told them not to fear the end of the world but, “when these things begin to take place, straighten up and raise your heads, because redemption is drawing near.” (Luke 21:28) About the only thing he never told them about his second coming was when it would all happen.
But what about the people of the Old Testament? They had not even experienced Jesus’ first coming, how could they imagine his second coming? Isaiah gives us some clues in the verse printed above.
As Isaiah says, the people of the Old Testament knew that someday the heavens and earth will vanish and wear out: “Lift up your eyes to the heavens, and look at the earth beneath; for the heavens vanish like smoke, the earth will wear out like a garment.”
They could imagine the destruction of the entire world because they knew the story of the great worldwide flood in the days of Noah, how God destroyed everyone and everything except Noah, his family and the animals with him on the ark.
Isaiah also speaks about the destruction of the world back in Isaiah 34:4: “All the host of heaven shall rot away, and the skies roll up like a scroll. All their host shall fall, as leaves fall from the vine, like leaves falling from the fig tree.”
There is also Psalm 102:26: “They will perish, but you will remain; they will all wear out like a garment. You will change them like a robe, and they will pass away.”
So it was well-known among the people of the Old Testament that someday the heavens and the earth would perish.
According to the prophet Joel, they also knew that there would be signs of the end: Joel 2:30–32: “And I will show wonders in the heavens and on the earth, blood and fire and columns of smoke.  The sun shall be turned to darkness, and the moon to blood, before the great and awesome day of the LORD comes.  And it shall come to pass that everyone who calls on the name of the LORD shall be saved.”
The people of the Old Testament knew that the second coming of the Lord would mean Judgment Day:
Say among the nations, The LORD reigns! Yes, the world is established; it shall never be moved; he will judge the peoples with equity. Then shall all the trees of the forest sing for joy before the LORD, for he comes, for he comes to judge the earth.
He will judge the world in righteousness, and the peoples in his faithfulness. (Psalm 96:10, 12-13)
Isaiah chimes in with: “My arms will judge the peoples.” (Isaiah 51:5)
The people of the Old Testament also knew that, despite all the judgment and destruction, the believers would receive eternal life. As it says in the text: “But my salvation will be forever, and my righteousness will never be dismayed.
When it comes to the topic of forever in the Old Testament the book of Psalms is the place to go. Forever and eternity are mentioned over 120 times in the Book of Psalms, more than any other book of the entire Bible.
There is Psalm 23: “Surely goodness and mercy will follow me all the days of my life and I will dwell in the house of the Lord forever.”
And Psalm 121: “The Lord will watch over your going out and your coming in from this time forth and forevermore.”
There is the well-known passage from Job 19:25–27: “For I know that my Redeemer lives, and at the last he will stand upon the earth.  And after my skin has been thus destroyed, yet in my flesh I shall see God,  whom I shall see for myself, and my eyes shall behold, and not another. My heart faints within me!”
So even though the people of the Old Testament had not even experienced the first coming of the Lord they already were well acquainted with things related to the second coming of the Lord, that the heaven and earth would pass away, there would be judgment, but that God’s salvation would last forever.
And through it all the prophets did what all Scripture teaches us to do; to trust in the Lord. He is the only one that can keep us strong in the days to come.
Jude 24-25 says, “Now to him who is able to keep you from stumbling and to present you blameless before the presence of his glory with great joy,  to the only God, our Savior, through Jesus Christ our Lord, be glory, majesty, dominion, and authority, before all time and now and forever.”
The fact that God is the one who keeps us from stumbling implies that we have been made to stand. You can’t stumble unless you have first been raised up to your feet. And in Christ we have been made to stand, to stand in the grace and mercy of God.
As Jesus says in Mark 13:31, “Heaven and earth will pass away but my words will not pass away.”
Even though they had way fewer details about the end of the world, there is no doubt that the people of the Old Testament had the same faith that we do. They knew that heaven and earth would wear out and be gone. They knew God’s salvation through faith in the Messiah would last forever. And best of all they knew, as we do, that they were God’s beloved children till the end of this world and on into eternity.