Once Saved, Always Saved? How About Works?

Many modern Christians believe in the doctrine known as “eternal security” (commonly known as “once saved, always saved”). But is this belief scriptural? Let’s allow the scriptures to speak for themselves.
“I mention it that you may be saved.” (John 5:34 NIV). Salvation is not guaranteed to everyone, or anyone. See Mt 7:21-23.
“For in this hope you were saved.” (Romans 8:24 NIV). In one sense, salvation is past tense.
“It is by grace you have been saved.” (Ephesians 2:5 NIV).