Question:
Once you are saved, do you have eternal security, or can you lose your salvation?

Answer:

If you are truly trusting in the finished work of Christ alone for your soul’s salvation, you can be assured that you will never lose that salvation.  “Whosoever believeth…[has] everlasting life” (John 3:16).  It is not everlasting if one can lose it.  “My sheep hear My voice, and I know them, and they follow me; and I give unto them eternal life; and they shall never perish, neither shall any man pluck them out of My hand.  My Father, which gave them Me, is greater than all; and no man is able to pluck them out of My Father’s hand” (John 10:27-29).  “These things have I written unto you…that ye may know that ye have eternal life [who] believe on the name of the Son of God” (1 John 5:13).