Once Saved, Always Saved?
Sorry, but that's simply not true.
If you think that "being saved" is a one-off thing, you're mistaken. We're asked to do works of obedience (repentance).
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.
- Ezekiel 18:24 (KJV)
Some that are saved, and written in the book (of life), will be blotted out again.
Let them be blotted out of the book of the living, and not be written with the righteous.
- Psalms 69:28 (KJV)
Faith without works (of obedience, repentance) is dead.
For as the body without the spirit is dead, so faith without works is dead also.
- James 2:26 (KJV)
Still don't believe me?
Not every one that saith unto me, Lord, Lord, shall enter into the kingdom of heaven; but he that doeth the will of my Father which is in heaven. 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? And then will I profess unto them, I never knew you: depart from me, ye that work iniquity.
- Matthew 7:21-23 (KJV)
The Bible specfically says that some will depart from the faith.
Now the Spirit speaketh expressly, that in the latter times some shall depart from the faith, giving heed to seducing spirits, and doctrines of devils; speaking lies in hypocrisy; having their conscience seared with a hot iron; forbidding to marry, and commanding to abstain from meats, which God hath created to be received with thanksgiving of them which believe and know the truth.
- 1 Timothy 4:1-3 (KJV)
This is serious stuff, and we ought to take repenting seriously.
For if we sin wilfully after that we have received the knowledge of the truth, there remaineth no more sacrifice for sins, but a certain fearful looking for of judgment and fiery indignation, which shall devour the adversaries.
- Hebrews 10:26-27 (KJV)
Even the parable of the Sower clearly shows that we can lose our salvation under tribulation or persecution.
Hear ye therefore the parable of the sower. When any one heareth the word of the kingdom, and understandeth it not, then cometh the wicked one, and catcheth away that which was sown in his heart. This is he which received seed by the way side. But he that received the seed into stony places, the same is he that heareth the word, and anon with joy receiveth it; Yet hath he not root in himself, but dureth for a while: for when tribulation or persecution ariseth because of the word, by and by he is offended. He also that received seed among the thorns is he that heareth the word; and the care of this world, and the deceitfulness of riches, choke the word, and he becometh unfruitful. But he that received seed into the good ground is he that heareth the word, and understandeth it; which also beareth fruit, and bringeth forth, some an hundredfold, some sixty, some thirty.
- Matthew 13:18-23 (KJV)
Even David was scared of losing his salvation.
Cast me not away from thy presence; and take not thy holy spirit from me.
- Psalm 51:11 (KJV)