People who are sure they have been born again
are promised (in the NT) that they will gain heaven.
"How can I be sure that my faith is a genuine and saving one?
"The answer is, Test it. Make certain that it is the, “faith of God’s elect” (Titus 1:1). Ascertain whether or not your faith is accompanied with those fruits which are inseparable from a God-given and Spirit-wrought faith.
"Probably many are ready to say, There is no need for me to be put to any such trouble; I know that my faith is a saving one, for I am resting on the finished work of Christ. But dear friend, it is foolish to talk like that. God Himself bids His people to make their “calling and election sure” (2 Peter 1:10). Is that a needless exhortation? O pit not your vain confidence against Divine wisdom.
"It is Satan who is striving so hard to keep many from this very task, lest they discover that their house is built on sand. There is hope for one who discovers his illusion, but there is none for those who go on believing the Devil’s lie, and rest content with the very real but false peace which he gives to so many of his poor victims.
"God Himself has supplied us with tests, and we are mad if we do not avail ourselves of them, and honestly measure ourselves by them. “These things have I written unto you that believe on the name of the Son of God, that ye may know that ye have eternal life, and that ye may believe (more intelligently) on the name of the Son of God” (1 John 5:13).
"The Holy Spirit Himself moved one of His servants to write a whole Epistle to instruct as how we might know whether or not we have eternal life. Does that look as though the question may be determined and settled as easily as so many present-day preachers and writers represent it? If nothing more than a firm persuasion of the truth of John 3:16 or 5:24 be needed to assure me of my salvation, then why did God give a whole Epistle to instruct us on this subject?
"Let the really concerned soul read slowly and thoughtfully through this first Epistle of John, and let him duly observe that not once in its five chapters are we told, “We know that we have passed from death unto life because we are resting on the finished work of Christ.” The total absence of such a statement ought, surely, to convince us that something must be radically wrong with so much of the popular teaching of the day on this subject.
"But not only is there no such declaration made in this Epistle, the very first passage which contains the familiar “we know” is quite the reverse of what is now being so widely advocated as the ground of Christian assurance. “And hereby we do know that we know Him, if we keep His commandments” (1 John 2:3). Is not that plain enough? A godly life is the first proof that I am a child of God."
From:
http://sovereigngrace.ddns.net:81/Assurance1-Pink.html