Verses used to teach this doctrine:

1.           John 10:29

My Father, who has given them to Me, is greater than all; and no one is able to snatch them out of the Father's hand

2.           Romans 8:35-39

For I am convinced that neither death, nor life, nor angels, nor principalities, nor things present, nor things to come, nor powers,  nor height, nor depth, nor any other created thing, shall be able to separate us from the love of God, which is in Christ Jesus our Lord. (Verses 38-39) - Note: Jude 21

3.           1 John 3:9

No one who is born of God practices sin, because His seed abides in him; and he cannot sin, because he is born of God.

If absolutely so, then what about:

-      Judas

-      Simon the Sorcerer (Acts 8:13-24)

-      Peter (Galatians 2)

Think of Implication:

     Become a Christian, then “eat, drink, and be merry”

Verses that teach one can fall away:

1.           2 Peter 2:20-22

For if after they have escaped the defilements of the world by the knowledge of the Lord and Savior Jesus Christ, they are again entangled in them and are overcome, the last state has become worse for them than the first. (Verse 20)

2.           2 Peter 1:10

Therefore, brethren, be all the more diligent to make certain about His calling and choosing you; for as long as you practice these things, you will never stumble;

3.           Revelation 2:4-5

But I have this against you, that you have left your first love. Remember therefore from where you have fallen, and repent and do the deeds you did at first; or else I am coming to you, and will remove your lampstand out of its place-- unless you repent.

4.           1 Corinthians 9:27

but I buffet my body and make it my slave, lest possibly, after I have preached to others, I myself should be disqualified.

5.           Hebrews 3:12

Take care, brethren, lest there should be in any one of you an evil, unbelieving heart, in falling away from the living God.

6.           1 Corinthians 10:12

Therefore let him who thinks he stands take heed lest he fall.

7.           Galatians 5:4

You have been severed from Christ, you who are seeking to be justified by law; you have fallen from grace.

-      There are 2500 warnings in the Bible concerning the possibility of falling away.  Why are they there if such is impossible to do?