Consider the following quote from A.W. Tozer:

   "One distinguishing mark of those first Christians was a supernatural radiance that shined out from within them.  The sun had come up in their hearts and its warmth and light made unnecessary any secondary sources of assurance.  They had the inner witness.  They knew with an immediate awareness that required no jockeying of evidence to give them a feeling of certainty.  Great power and great grace marked their lives, enabling them to rejoice to suffer shame for the name of Jesus.

   It is obvious that the average evangelical ['christian'] today is without this radiance.  The efforts of some of our teachers to cheer up our drooping saints are futile because those same teachers reject the very phenomenon that would naturally produce joy, namely, the inner witness.  In their strange fear of the relgious emotions they have explained away the Scriptures that teach this witness, such as, 'The Spirit itself beareth witness' and 'He that believeth on the Son of God hath the witness in himself.'

   Instead of the inner witness we now substitute logical conclusions drawn from texts.  A conversation between a seeker and a worker in an inquiry room is likely to run about like this:  'Do you want the Lord to receive you and make you His child?' 'Yes.' 'Well, read this:  "Him that cometh to me I will in no wise cast out."  Do you believe that?'  'Yes.'  'Now if He doesn't cast you out, what does He do?'  'I suppose He takes me in.'  'Amen.  Now He has taken you in and you are His child.  Why don't you tell others about it.'  So the bewildered seeker forces a waxy smile and testifies that he has been converted to Christ.  He is honest and means well but he has been led astray.  He has fallen victim to a Spiritless syllogism.  There is no witness, no immediacy of knowledge, no encounter with God, no awareness of inner change.

   Where there is a divine act within the soul there will always be a corresponding awareness.  This act of God is self-validating.  It is its own evidence and addresses itself direct to the religious consciousness.  Abundant external evidence may exist that a work has been done within, and in this the reason may rejoice; but such evidence cannot be sufficient to guarantee that a saving work has been wrought.  Whatever can be judged by reason is subject to the limitations and errors of reason.  God waits to assure us that we are His children in a manner that eliminates the possibility of error, that is, by the inner witness."

(A.W. Tozer, Born After Midnight, p. 13-14)

Here are some verses on the inner witness:

Romans 8:16:  "The Spirit itself beareth witness with our spirit, that we are the children of God"

1 John 4:13:  "Hereby know we that we dwell in him, and he in us, because he hath given us of his Spirit"

1 John 3:24:  "And he that keepeth his commandments dwelleth in him, and he in him. And hereby we know that he abideth in us, by the Spirit which he hath given us."

   A pastor asking members of the congregation to raise their hands if they can give a Bible reason for going to heaven is a completely false and misguided approach as the above Bible verses and Tozer's explanation point out.  Tozer further writes "When Jesus was here upon the earth and walked among us, He used no fancy evangelistic maneuvers.  He never said, 'Now raise your hand; now put it down!'"  (A.W. Tozer Faith Beyond Reason p. 46-47)  The question to ask would be whether or not a person knows that he has the Inner Witness, the Holy Spirit.  
   Now, what if someone does have the Inner Witness, is there eternal security for that person?  Is he guaranteed a home in heaven?  The Bible pictures us as becoming one with the Lord Jesus Christ (as in marriage).  He saves us by becoming one with us.  1 John 1:2  calls the Lord Jesus "that eternal life".  It is only if we are in the Lord, one with the Lord that we have eternal life.  Jesus said  “I am the resurrection, and the life” (John 11:25)  God won't divorce us, but we can divorce Him.
Consider these Bible verses: 
Hebrews 6:4-6:  "For it is impossible for those who were once enlightened, and have tasted of the heavenly gift, and were made partakers of the Holy Ghost, And have tasted the good word of God, and the powers of the world to come, If they shall fall away, to renew them again unto repentance; seeing they crucify to themselves the Son of God afresh, and put him to an open shame.
Mark 13:13:  "And ye shall be hated of all men for my name's sake: but he that shall endure unto the end, the same shall be saved."

Mark 4:13-20:  "And he said unto them, Know ye not this parable? and how then will ye know all parables? The sower soweth the word. And these are they by the way side, where the word is sown; but when they have heard, Satan cometh immediately, and taketh away the word that was sown in their hearts. And these are they likewise which are sown on stony ground; who, when they have heard the word, immediately receive it with gladness; And have no root in themselves, and so endure but for a time: afterward, when affliction or persecution ariseth for the word's sake, immediately they are offended.  And these are they which are sown among thorns; such as hear the word, And the cares of this world, and the deceitfulness of riches, and the lusts of other things entering in, choke the word, and it becometh unfruitful.  And these are they which are sown on good ground; such as hear the word, and receive it, and bring forth fruit, some thirtyfold, some sixty, and some an hundred."

2 Peter 2:20, 21:  "For if after they have escaped the  pollutions of the world through the knowledge of the Lord and Saviour Jesus  Christ, they are again entangled therein, and overcome, the latter end  is worse with them than the beginning.  For it had been better for them not to have known the way of righteousness, than, after they have known it, to turn from the holy commandment delivered unto them. "

Revelation 3:21:  "To him that overcometh will I grant to sit with me in my throne, even as I also overcame, and am set down with my Father in his throne."
John 15:5-6:  "....I am the vine, ye are the branches: He that abideth in me, and I in him, the same bringeth forth much fruit: for without me ye can do nothing. "If a man abide not in Me, he is cast forth as a branch, and is  withered; and men gather them, and cast them into the fire, and they are  burned." 
Romans 11:21-22:  "....For if God spared not the natural  branches, take heed lest he also spare not  thee.  Behold therefore the goodness and severity of God: on them which fell, severity; but toward thee, goodness, if thou continue in his goodness: otherwise thou also shalt be cut off."

1Cor. 3:16-17:  "....Know ye not that ye are the temple of God, and that the Spirit of God dwelleth in you?  If any man defile the temple of God, him shall God  destroy; for the temple of God is holy, which temple ye are..."

Colossians 1:21-23:  “And you, that were sometime alienated and enemies in your mind by wicked works, yet now hath he reconciled In the body of his flesh through death, to present you holy and unblameable and unreproveable in his sight: If ye continue in the faith grounded and settled, and be not moved away from the hope of the gospel, which ye have heard, and which was preached to every creature which is under heaven; whereof I Paul am made a minister;”

1 Timothy 1:5-7:  “From which some having swerved have turned aside unto vain jangling;”

1 Timothy 1:18-20:  “This charge I commit unto thee, son Timothy, according to the prophecies which went before on thee, that thou by them mightest war a good warfare; Holding faith, and a good conscience; which some having put away concerning faith have made shipwreck: Of whom is Hymenaeus and Alexander; whom I have delivered unto Satan, that they may learn not to blaspheme.”

Jude 12:  “These are spots in your feasts of charity, when they feast with you, feeding themselves without fear: clouds they are without water, carried about of winds; trees whose fruit withereth, without fruit, twice dead, plucked up by the roots;”
1 John 5:16:  "If any man see his brother sin a sin which is not unto death, he shall ask, and he shall give him life for them that sin not unto death. There is a sin unto death: I do not say that he shall pray for it."

11 Chronicles 14-16 - read the story of King Asa
Philippians 2:12:  “work out your own salvation with fear and trembling.”

If there is no need to be faithful to the end, than why would all the martyrs down through the centuries have died – why bother?  Revelation 2:10b:  “be thou faithful unto death, and I will give thee a crown of life.”

Some of the churches in Revelation 2 and 3 are warned to repent - read it and see the consequences for not repenting.
Ezekiel 21-30 - "But if the wicked will turn from all his sins that he hath committed, and keep all my statutes, and do that which is lawful and right, he shall surely live, he shall not die.  All his transgressions that he hath committed, they shall not be mentioned unto him: in his righteousness that he hath done he shall live. Have I any pleasure at all that the wicked should die? saith the Lord GOD: and not that he should return from his ways, and live?  But when the righteous turneth away from his righteousness, and committeth iniquity, and doeth according to all the abominations that the wicked man doeth, shall he live? All his righteousness that he hath done shall not be mentioned: in his trespass that he hath trespassed, and in his sin that he hath sinned, in them shall he die.  Yet ye say, The way of the LORD is not equal. Hear now, O house of Israel; Is not my way equal? are not your ways unequal?  When a righteous man turneth away from his righteousness, and committeth iniquity, and dieth in them; for his iniquity that he hath done shall he die.  Again, when the wicked man turneth away from his wickedness that he hath committed, and doeth that which is lawful and right, he shall save his soul alive.  Because he considereth, and turneth away from all his transgressions that he hath committed, he shall surely live, he shall not die.  Yet saith the house of Israel, The way of the LORD is not equal. O house of Israel, are not my ways equal? are not your ways unequal?  Therefore I will judge you, O house of Israel, every one according to his ways, saith the Lord GOD. Repent, and turn yourselves from all your transgressions; so iniquity shall not be your ruin.