Romans 6:23: For the wages of sin is death; but the gift of God is eternal life through Jesus Christ our Lord. Ask yourself, is a gift free? Who pays for a gift the giver or the receiver? Who had to pay for our eternal life? How did it get paid? How many times do you have to receive eternal life as a free gift for it to last forever? If you believe you can lose your salvation, you will end up working and putting your effort into doing, or not doing that you think makes you lose your salvation, like committing big sins of adultery, or even worse. When you are done living your life, you die and you meet God, you are telling God he is in DEBT and owes it to you to save you from burning in hell, because of SOMETHING YOU DID here on earth to try to keep your salvation. Does the bible says God owes us anything? Is there a single promise in the bible for partial faith in Christ, and partially in your good works, or giving up sins to save you? The promise is for those who ONLY believe ON Jesus for salvation. Lets take a look at what Jesus is going to say to the best christians out there, who failed to trust ON Jesus olny, but relied in their good works to save them: Matthew 7:22 "Many will say to me in that day, Lord, Lord, have we not prophesied in thy name? and in thy name have cast out devils? and in thy name done many wonderful works? Mat 7:23 And then will I profess unto them, I never knew you: depart from me, ye that work iniquity." Notice, it doesn't say I used to know you and you lost your salvation because of a big sin, he NEVER knew you, that means you were never born again(saved) to begin with. Lets look at a verse where the bible clearly states the believer CAN KNOW he has everlasting life, which means he can be 100% sure he is saved, and on his way to heaven. 1 john 5:13 "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 on the name of the Son of God." If you don't believe you have eternal life this moment, and that you are saved forever, and must do something to keep your salvation, you are making God a liar, because he said we can know, I will throw a few more verses in to show that salvation is by faith only!
John 3:36 He that believeth on the Son hath everlasting life: and he that believeth not the Son shall not see life; but the wrath of God abideth on him. Ephesians 2:8,9 we are told, “For by grace are ye saved through faith; and that not of yourselves: it is the gift of God: Not of works, lest any man should boast.” Now, lets look at what God thinks of your self effort toward getting into heaven by your good works, or giving up sins!
Isaiah 64:6
But we are all as an unclean thing, and all our righteousnesses are as filthy rags; and we all do fade as a leaf; and our iniquities, like the wind, have taken us away.