The devil does not give up on a person simply because he gains faith, obeys the gospel and begins behaving as a disciple of Christ.
Simon the sorcerer was all of those things, yet his greed and selfish ambition were easily provoked by the tempter. His heart was not right with God for he was again “in the gall of bitterness and in the bond of iniquity” (Acts 8:23). If a man is saved by trusting faith, surely Simon proved that he can so sin as to be returned to peril (Second Peter 2:20-22).
There is a sense in which salvation is something accomplished for the disciple, but yet another sense in which it is still being executed, and still another sense in which it is yet future.
The Christian has been saved from the guilt of his past sins and the penalty due them. When he repents and turns to Christ according to the New Testament, God wipes the slate clean and forgives him every trespass (Hebrews 8:12, 10:17). Even a sinful woman of the city could be told, “Your sins are forgiven … Your faith has saved you; go in peace” (Luke 7:48, 50). It is God “who saved us and called us to a holy calling” by “the standard of teaching to which you were committed” (Second Timothy 1:9, Romans 6:17).
Saved.
But.
We are still the subjects of an ongoing, seemingly endless rescue operation, made necessary by our foolish forays back into the realm of temptation and sin. “Therefore, my beloved, as you have always obeyed, so now, not only as in my presence but much more in my absence, work out your own salvation with fear and trembling, for it is God who works in you, both to will and to work for his good pleasure” (Philippians 2:12-13).
Our salvation is still being worked out as we learn to allow God to work through our hands instead of lending them to the devil. We are “saved through sanctification by the Spirit and belief in the truth” as we become increasingly set apart from the world for a purpose higher even than our own (Second Thessalonians 2:13; cf. Romans 12:1-2).
We must remain vigilant and ready for there remains a sense in which salvation is wholly future, awaiting the return of Jesus in the clouds as Judgment Day dawns. “Besides this you know the time, that the hour has come for you to wake from sleep. For salvation is nearer to us now than when we first believed. The night is far gone; the day is at hand. So then let us cast off the works of darkness and put on the armor of light” (Romans 13:11).
While no one can snatch us out of Christ’s hand, we surely have the potential to jump, unless “we are not of those who draw back to perdition, but of those who believe to the saving of the soul” (Hebrews 10:39).