The Divine Guarantee of an Eternal Salvation

“If, as some Christians maintain, salvation can be forfeited, it then would be obvious that God’s grace lacks everlasting power, that the life He bestows on believers is not eternal. A believer’s hope could only be temporary. He would be in continual danger of losing salvation, because it would be dependent on his own faithfulness and power to avoid sin that would cast him back into lostness. If that were true, one’s own power to sin would be greater than God’s power to save, and any testimony given to unbelievers to bring them to salvation would be undermined.”

 – John MacArthur
Titus MacArthur New Testament Commentary p.108