⁶ And the Lord added to the church daily those who were being saved. This clearly shows that being saved is not instantaneous with believing, baptizing, and joining the church; no, they were described as were being saved — as a process with an end in the future, at the death of their selfish spirit on the cross.  This was the church of the Apostles; people were not saved instantly, even when the Apostles could lay hands on them and speak from the Spirit of God. Further evidence that being saved is not instant, but a process of carrying your cross is: For the message of the cross is foolishness to those who are perishing, but to us who are being saved it is the power of God. 1 Cor 1:18

Paul further shows that believing and salvation do not occur simultaneously in his letters to believers in the churches.

1. now is our salvation nearer than when we first believed, Rom 13:11
2. continue to work out your salvation with fear and trembling, Phil 2:12
3. For we are saved by hope; but hope that is seen is not hope. For who hopes for what he has already seen? But if we hope for that we do not yet see, then we wait for it [salvation] with patient endurance. Rom 8:24-25
4. But let us, who are of the day, be sober, putting on the breastplate of faith and love; and for a helmet, the hope of salvation. 1 Thes 5:8
5. For the message of the cross is foolishness to those who are perishing, but to us who are being saved it is the power of God. 1 Cor 1:18
   (While in the inward cross of self-denial, you will see the sin slowly disappear from your life until you are free of sin.)
6. godly sorrow produces repentance that leads to salvation, 2 Cor 7:10
7. do not grieve the holy Spirit of God, by whom you are sealed unto the day of redemption [future happening]. Eph 4:30
   (Paul is speaking to believers in the church who have not yet been redeemed, which is salvation.)
8. For we are the sweet aroma of Christ unto God, to those who are being saved. 2 Cor 2:15
9. we are made partakers of Christ, if we hold firm the beginning of our confidence to the end. Heb 3:14
10. For you need endurance in order to do God’s will, so that after you may receive the promise. Heb 10:36
11. we desire that every one of you show the same diligence in realizing the full assurance of hope to the end.
    So that you are not slothful, but followers of those who through faith and patience inherit the promises. Heb 6:11-12

And Peter echoes the same message that salvation is not just believing or faith, rather salvation is the end of faith's obedient journey and requires growth:

Who are kept by the power of God through faith to salvation ready to be revealed in the last time.
In that greatly rejoice though it is necessary to suffer a few griefs through various trials,
so that the trial of your faith, being much more precious than gold that perishes,
though it is tried with fire, might result in praise and honor and glory at the appearing of Jesus Christ.
Though you have not seen him, you love him; though you do not see him now,
but believe in him, you rejoice with joy that is unspeakable and full of glory,
Receiving the end of your faith — the salvation of your souls. 1 Pet 1:5-9

As newborn babies, desire the sincere milk of the word, so that you may grow up to salvation, 1 Pet 2:2

Salvation occurs when you experience the grace of God (Christ) bring it to you, when Christ destroys the selfish spirit in you by the spirit in his mouth and by the brightness of his coming, when he crushes the head of Satan under your feet, [a personal experience with your feet and Christ], and when you enter union with Him.

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