When Jesus Christ died on the cross “he became the author of eternal salvation unto all them that obey Him.” (He 5:9) He does not offer a temporary salvation, but an eternal one.
By definition, salvation from Hell must be eternal, for if one ever ends up in Hell there can be no real sense in which one has ever been saved from it. In other words, a salvation that can be lost is no salvation at all.
Yet many complain that eternal salvation – the once saved always saved kind – means we can “get saved” and then live like the devil. But this is not salvation at all; God saves from the dominion of sin as well as from its penalty (Ro 6:14), such that the saved obey Christ as new creatures, with a new nature. This renewing of our hearts is not by the will of Man (Jn 1:12-13); it is the work and gift of God. (Ep 2:8-10)
If salvation can be lost, the question to ask is, “How good do I have to be to keep it?” The question has only one safe answer: “Be perfect.” (Mt 19:20-21) We dare not presume a lower standard, and there is no higher one … yet it implies we can never know we have salvation.
But those who trust in Christ know they have eternal life (1Jn 5:13), and that it is not dependent on their works in any way. (Ro 4:5) They know God is able to keep them from falling and to present them faultless before Him. (Jud 1:24)
Those who don’t have an eternal salvation have not yet grasped the significance of the cross; Christ’s work is an efficacious, limited atonement for all — He did not merely make salvation a possibility for all, He has infallibly saved all who believe (He 7:25); their eternal end is already certain. (Ro 8:30)
“Give diligence to make your calling and election sure.” (2Pe 1:10) Once Jesus Christ pays your sin debt, you will never be condemned … ever. (Ro 4:6-8) Once we see the power of His cross we cannot doubt its efficacy, and we come to understand the only salvation there is … an eternal one. (He 7:25)