Question:

Once a person accepts Jesus Christ as Lord and Savior, is his salvation assured, making the adage “once saved, always saved” true?

Answer:

We believe the Bible teaches eternal security–in other words, once saved
always saved–for one simple reason. It is God who saves us when we put our
trust in Him by faith alone in Christ alone. There’s nothing we can do to
earn our salvation (Eph. 2:8-9). Because God is the one who saves, our
salvation cannot be undone. Romans 8:38-39 speaks to this very clearly.

Perhaps the strongest passage about our security in Christ is John 6:35-37,
where Jesus says, “However, those the Father has given me will come to me,
and I will never reject them.”

There are a couple of passages (Hebrews 10:26 comes to mind) that seem to
indicate that we can lose our salvation. But when you read this verse
carefully, you can see that it is those who come to a knowledge of Christ
and then refuse to follow Him who are held accountable. Knowledge alone
doesn’t save, but knowing and then continuing to refuse to receive the gift
of salvation could lead to a hardening of the heart.