How does Isaiah 65:20 assure us that God’s people will enjoy security?

Isaiah chapter 65 prophetically describes conditions that we will enjoy if we have Jehovah’s approval to live when he, in the final sense, creates these new heavens and new earth.

Those blessed with a lasting place in the new earth will not grow old and inevitably die.

Isaiah 65:20 assures us: “No more will there come to be a suckling a few days old from that place, neither an old man that does not fulfill his days; for one will die as a mere boy, although a hundred years of age; and as for the sinner, although a hundred years of age he will have evil called down upon him.”

In the coming new world, people will be safe, secure, able to enjoy life. If a person chooses to rebel against God, he will not be allowed to continue living. God will remove him. What if the rebellious sinner is a hundred years old? He will die “as a mere boy” compared to having endless life.—1 Timothy 1:19, 20; 2 Timothy 2:16-19.

That is a lovely chapter! It assures God's covenant people that God will create new heavens and a new earth; the former things will not be remembered, nor will they come to mind. God will create Jerusalem to be a delight and its people a joy, (verses 1-2) and then it goes on to describe the earthly conditions for God's covenant people.

The assurance lies in knowing that this promise to His covenant people is an everlasting promise. It was given centuries ago, but it will come true, for all Israel will yet be saved, as the Bible states in Romans chapter 11 verses 25-32. The covenant mentioned there in Romans ch. 11 deals with how God takes away their sins. See Zechariah 13:1.

The day is coming when those in the new covenant (the one where our sins are taken away) will enjoy the glorious new heavens and the new earth that God will bring to pass - in which righteousness will dwell - 2 Peter 3:10-13.

AiH

"There shall be no more thence an infant of days, nor an old man that hath not filled his days: for the child shall die an hundred years old; but the sinner being an hundred years old shall be accursed."

That wacky Bible.

That is one of the prophecies of the bible.

It basically says that if no more people die before adulthood, no more babies die a slow and horrible death, then there probably is a god.

Prophecies that can interpreted anyway you want has no meaning.