The answer is really in the context:
Acts 2:37 Now when they heard this, they were pricked in their heart, and said unto Peter and to the rest of the apostles, Men and brethren, what shall we do? 38 Then Peter said unto them, Repent, and be baptized every one of you in the name of Jesus Christ for the remission of sins, and ye shall receive the gift of the Holy Ghost. 39 For the promise is unto you, and to your children, and to all that are afar off, even as many as the Lord our God shall call. 40 And with many other words did he testify and exhort, saying, Save yourselves from this untoward generation.
The gift of the Holy Spirit is not available today because it was given not at baptism but by the subsequent laying on of the Apostles’ hands (Acts 8:18). There are no Apostles today. The gift of the Holy Spirit is not essential for salvation.
Jesus’ instructions to his apostles:
Mark 16:15 And he said unto them, Go ye into all the world, and preach the gospel to every creature.16 He that believeth and is baptized shall be saved...
From this the sequence is:
1. Hear the Gospel
2. Believe the Gospel
3. Be baptised
At Pentecost the Jews asked Peter what they were required to do:
Acts 2:38 Then Peter said unto them, Repent, and be baptized every one of you in the name of Jesus Christ for the remission of sins,
Baptism then is for the remission of our sins so it follows that we must recognise our sins and turn from them before baptism. To our sequence, between believing and baptism, we need to add repent.
The sequence becomes:
1. Hear the Gospel
2. Believe the Gospel
4. Be baptised
Baptism by immersion in water is an essential beginning to salvation.
Jesus was baptised:
Matthew 3:15 And Jesus answering said unto him, Suffer it to be so now: for thus it becometh us to fulfil all righteousness. Then he suffered him.
The Philippian Jailer was baptised:
Acts 16:30 And (he) brought them out, and said, Sirs, what must I do to be saved? 31 And they said, Believe on the Lord Jesus Christ, and thou shalt be saved, and thy house. 32 And they spake unto him the word of the Lord, and to all that were in his house. 33 And he took them the same hour of the night, and washed their stripes; and was baptized, he and all his, straightway.
The Samaritans were baptised:
Acts 8:12 But when they believed Philip preaching the things concerning the kingdom of God, and the name of Jesus Christ, they were baptized, both men and women.
Baptism is total immersion in water with the understanding that it is:
(1) For remission of sins
Acts 22:16 And now why tarriest thou? arise, and be baptized, and wash away thy sins, calling on the name of the Lord.
(2) A symbolic burial of the old man and a rising again to a newness of life.
Romans 6:4 Therefore we are buried with him by baptism into death: that like as Christ was raised up from the dead by the glory of the Father, even so we also should walk in newness of life.
From this the sequence becomes:
1. Hear the Gospel
2. Believe the Gospel
4. Be baptised
5. Walk in newness of life
Paul gives this advice:
Romans 6:19... as ye have yielded your members servants to uncleanness and to iniquity unto iniquity; even so now yield your members servants to righteousness unto holiness.
Romans 12:1 I beseech you therefore, brethren, by the mercies of God, that ye present your bodies a living sacrifice, holy, acceptable unto God, which is your reasonable service. 2 And be not conformed to this world: but be ye transformed by the renewing of your mind, that ye may prove what is that good, and acceptable, and perfect, will of God.
Peter gives the same advice:
1Peter 4:1 Forasmuch then as Christ hath suffered for us in the flesh, arm yourselves likewise with the same mind: for he that hath suffered in the flesh hath ceased from sin; 2 That he no longer should live the rest of his time in the flesh to the lusts of men, but to the will of God.
We will be saved only if we endure to the end of our lives.
Matthew 24:13 But he that shall endure unto the end, the same shall be saved.
Salvation has to be worked out with fear and trembling.
Philippians 2:12 Wherefore, my beloved, as ye have always obeyed, not as in my presence only, but now much more in my absence, work out your own salvation with fear and trembling.
Paul was aware that even he could fall away.
1Corinthians 9:27 But I keep under my body, and bring it into subjection: lest that by any means, when I have preached to others, I myself should be a castaway.
The doctrine of ‘once saved always saved’ is not taught in scripture.
Understand the word of God
What we understand and believe is the basis of our ‘faith’ and has one source – scripture.
Romans 10:17 So then faith cometh by hearing, and hearing by the word of God.
Only by a careful reading of scripture can we come to an understanding of the truth. There are many churches with different doctrines and gospels and it is obvious that they can’t all be teaching the truth. We have to test all by the Bible.
The ‘Gospel’ (as we see from Acts 8:12 above) consists of the things concerning the kingdom of God, and the name of Jesus Christ.
The kingdom of God is to be set up on earth - salvation does not involve going to Heaven. At death we go to the grave and return to dust.
Ecclesiastes 3:20 All go unto one place; all are of the dust, and all turn to dust again.
We have no conscious existence after death.
Ecclesiastes 9:5 For the living know that they shall die: but the dead know not any thing...
Psalms 146:4 His breath goeth forth, he returneth to his earth; in that very day his thoughts perish.
We do not go to heaven.
John 3:13 And no man hath ascended up to heaven...
Acts 2:34 For David is not ascended into the heavens...
We die because we sin.
Ezekiel 18:4 Behold, all souls are mine; as the soul of the father, so also the soul of the son is mine: the soul that sinneth, it shall die.
Romans 6:23 For the wages of sin is death;
The dead 'sleep' in the dust of the earth. The only way we can 'survive' death is by resurrection.
Daniel 12:2 And many of them that sleep in the dust of the earth shall awake, some to everlasting life, and some to shame and everlasting contempt.
The TRUE HOPE of the gospel is resurrection from the dead to life in the kingdom of God. The kingdom of God on earth is the subject of Daniel’s prophecy.
Daniel 2:44 And in the days of these kings shall the God of heaven set up a kingdom, which shall never be destroyed: and the kingdom shall not be left to other people, but it shall break in pieces and consume all these kingdoms, and it shall stand for ever.
The angel Gabriel says of Jesus:
Luke 1:32 He shall be great, and shall be called the Son of the Highest: and the Lord God shall give unto him the throne of his father David: 33 And he shall reign over the house of Jacob for ever; and of his kingdom there shall be no end.
The kingdom of God is the restored kingdom of David, bearing rule over all the earth, which agrees with the prophecy of Isaiah:
Isaiah 9:6 For unto us a child is born, unto us a son is given: and the government shall be upon his shoulder: and his name shall be called Wonderful, Counsellor, The mighty God, The everlasting Father, The Prince of Peace. 7 Of the increase of his government and peace there shall be no end, upon the throne of David, and upon his kingdom, to order it, and to establish it with judgment and with justice from henceforth even for ever. The zeal of the LORD of hosts will perform this.
David by inspiration of the Holy Spirit says:
Psalm 37:11 But the meek shall inherit the earth; and shall delight themselves in the abundance of peace.
And Christ confirms it:
Matthew 5:5 Blessed are the meek: for they shall inherit the earth.
As God said to Moses:
Numbers 14:21 But as truly as I live, all the earth shall be filled with the glory of the LORD.
And through the prophet Habakkuk:
Habakkuk 2:14 For the earth shall be filled with the knowledge of the glory of the LORD, as the waters cover the sea.
Jesus promised his apostles:
Matthew 19:28 And Jesus said unto them, Verily I say unto you, That ye which have followed me, in the regeneration when the Son of man shall sit in the throne of his glory, ye also shall sit upon twelve thrones, judging the twelve tribes of Israel.
The name of Jesus Christ
Resurrection to eternal life is promised to those who believe and are baptised into the name of Jesus Christ. Only by association with the sacrifice of the life of Christ can we have our sins forgiven.
John 8:24 I said therefore unto you, that ye shall die in your sins: for if ye believe not that I am he, ye shall die in your sins.
Acts 4:12 Neither is there salvation in any other: for there is none other name under heaven given among men, whereby we must be saved.
The dead ‘in Christ’ are said to be ‘asleep’ until his return.
1 Thessalonians 4:13 But I would not have you to be ignorant, brethren, concerning them which are asleep, that ye sorrow not, even as others which have no hope... 15 For this we say unto you by the word of the Lord, that we which are alive and remain unto the coming of the Lord shall not prevent (precede) them which are asleep. 16 For the Lord himself shall descend from heaven with a shout, with the voice of the archangel, and with the trump of God: and the dead in Christ shall rise first: 17 Then we which are alive and remain shall be caught up together with them in the clouds, to meet the Lord in the air: and so shall we ever be with the Lord. 18 Wherefore comfort one another with these words.
Paul describes what is to happen:
1 Corinthians 15:22 For as in Adam all die, even so in Christ shall all be made alive. 23 But every man in his own order: Christ the firstfruits; afterward they that are Christ’s at his coming. 24 Then cometh the end, when he shall have delivered up the kingdom to God, even the Father; when he shall have put down all rule and all authority and power. 25 For he must reign, till he hath put all enemies under his feet. 26 The last enemy that shall be destroyed is death. 27 For he hath put all things under his feet. But when he saith all things are put under him, it is manifest that he is excepted, which did put all things under him. 28 And when all things shall be subdued unto him, then shall the Son also himself be subject unto him that put all things under him, that God may be all in all.
I hope you have found this helpful.