We have been told repeatedly that Paul took the gospel into the entire world from Acts 13 onwards, but in fact his custom was he most often spoke in the synagogue of the Jews to the Jews on the Sabbath days;

Act 17:1 And traveling through Amphipolis and Apollonia, they came to Thessalonica, where there was a synagogue of the Jews. 2 And according to Paul's custom, he went in to them and reasoned with them out of the Scriptures on three sabbaths, 3 opening and setting forth that Christ must have suffered, and to have risen again from the dead; and that this Jesus whom I preach to you is Christ. (cf. Lk.4:16)

Paul’s gospel to Israel was that the One they had crucified was their Messiah and this is what Paul preached from Acts 9 (9:20, 22) to Acts 28 (28:23). Read carefully Paul’s gospel of Acts 13:14‐41. This gospel has nothing to do with our “church” but is all about the promises made to Israel’s fathers and the focus being that the crucified One was raised to sit on David’s throne. Let us not be troubled that in this Jewish context; in this earthly purpose of God that forgiveness of sins and justification are freely proclaimed in Israel’s High Priest King. These consequences of our Lord’s crucifixion are not the exclusive preserve of the later calling given to Paul after Israel were set aside at Acts 28. Abraham was made righteous by faith, a joy found in Christ before the Law, see Roms.4:1‐14.

But wait, some Gentiles were saved in Acts 13. Surely this means the church which is His body had started? Absolutely not! Yes, a Gentile could be made righteous through faith by the gracious reckoning of God (see Roms.4:1‐14). The Righteousness and salvation freely available during Acts is not related to the “the Mystery [secret]” of “the body of Christ” as seen in Ephesians 1 and 3.

So why were Gentiles being saved during the Acts period?

Here is a summary. The Scriptures are clear, the Gentiles were saved and included in salvation during the Acts period according to the following;

1. The salvation of the Gentiles was anticipated historically. They had been included in salvation with Israel in the past;

Exo 12:48 And when a stranger shall stay with you, and desires to keep the Passover to Jehovah, let all his males be circumcised, and then let him come near and keep it. And he shall be as one that is born in the land. And no uncircumcised person shall eat of it. 49 There shall be one law to the native, and to the visitor that stays among you.

Israel was to be the light through which the world would be attracted to their God and Saviour. God did not change the dispensation just because Gentiles were saved in the Acts period. We Gentiles are not saved with Israel today; not graft into the Olive tree of Romans 11. The fact is that there is no National Israel today. There is but the “One New Man,” the creation first revealed in Paul’s first Post-Acts letter, Ephesians 2:15.

Since the Salvation of Gentiles was known of Israel in the OT and expected of Israel, how could it be “the Mystery (Grk. musterion, the Secret)”?

2. The salvation of the Gentiles was foretold by the Prophets. That Gentiles would be saved was clearly a fulfillment of prophecy;

Isa 49:6 And He said, It is but a little thing that You should be My servant to raise up the tribes of Jacob [Israel], and to bring back the preserved ones of Israel; I will also give You for a light to the nations [Non-Jews, Gentiles], to be My salvation to the end of the earth.

3. The salvation of the Gentiles during Acts was secondary to Paul’s ministry to Israel. Paul’s “missionary” journeys were “to the Jew first,” his custom was to preach in the synagogues on the Sabbath. He clearly tells us that Israel had an advantage during Acts;

Rom 1:16 For I am not ashamed of the gospel of Christ, for it is the power of God unto salvation to everyone who believes, to the Jew first and also to the Greek [i.e., the Gentile, non-Jew].

Rom 3:1 Then what is the superiority of the Jew? Or what is the profit of circumcision? 2 Much, by every way! Chiefly, indeed, because they were entrusted with the oracles [words] of God.

Paul’s gospel proclaimed Christ crucified, dead, and buried, but resurrected as Israel’s King to sit on David’s throne in Jerusalem. This is not the dispensational setting of today as revealed in Ephesians and Colossians. During Acts, Paul emphasized Israel’s Priest‐King; the Saviour, with forgiveness and righteousness.

4. The salvation of the Gentiles during Acts was whenever after the Jews rejected the message in specific locations. Peter was sent to Cornelius many years after Pentecost in Acts 10, after many years of Jewish rejection in the land. Paul went to “the Jews first” and when they rejected the message, then he turned to the Gentiles. Only on a few occasions did Paul preach to Gentiles independently of Israel or a Synagogue.

Act 13:46 But speaking boldly, Paul and Barnabas said, It was necessary for the Word of God to be spoken to you [Jews] first. But since indeed you put it far from you and judge yourselves unworthy of everlasting life, lo, we turn to the nations [non-Jews).

This is not the dispensational setting of today as revealed in the Post-Acts epistles of Ephesians and Colossians. The message today does not go to Jews first then to Gentiles afterwards. We preach Paul’s gospel to ALL Men of all races alike, without any distinction.

5. The salvation of the Gentiles during Acts followed God’s judgment on Israel which resulted in temporary blindness and stumbling. Sadly, we have been told repeatedly that Israel was cast aside at the cross. God saved a remnant of Israel at Pentecost. Yet the majority today believe it because repetition of an error appears to be truth only because it is repeated so often. The Word here clearly says Israel was not cast aside until Acts 28.

Rom 10:21 But to Israel He says, "All day long I have stretched forth My hands to a disobeying and gainsaying people."

Rom 11:1 I say then, Did not God put away His people? Let it not be said! For I also am an Israelite, of the seed of Abraham, of the tribe of Benjamin.

Rom 11:2 God did not thrust out His people whom He foreknew.

In Acts 9 a zealous Jew is struck with temporary blindness and stumbles then Peter preaches to a Gentile. In Acts 12 Israel’s King is struck dead and in Acts 13 a Jew is struck partially blind and he stumbles about, then Paul preaches to Jews and Gentiles. This was the condition of Israel nationally right through to the end of Acts, partially blinded and stumbling about and Gentiles were included because of it, see Romans 11:11. This is not the dispensational setting of today as revealed in Ephesians and Colossians; we Gentiles are not saved only because Israel is partially blinded and stumbling.

6. The salvation of the Gentiles during Acts was to make Israel jealous. If ever there was an Acts period dispensational truth which separated Paul’s Acts period ministry and writings from his post Acts ministry and writings it is this one.

Rom 11:11 I say then, have they stumbled that they should fall? Certainly not! But by their transgression (stumbling in some versions), salvation has come to the Gentiles, to provoke them to jealousy. (EMTV).

But today we are not saved to make Israel jealous. Note Paul’s apostleship during Acts was to the same end as shown here in Roms.11:13‐14. “If by any means I may provoke to emulation them [of Israel] which are my flesh, and might save some of them.”

7. The salvation of the Gentiles during Acts was according to prophesied, anticipating Israel’s restoration. It is a testimony to the strength of our bad religious traditions that many continue to think that the salvation of Gentiles during Acts must mean the start of something new. On the contrary, the prophetic announcements of Gentile inclusion also proclaimed the joyous restoration of Israel, not the bringing in of something completely different. Here is a passage from Amos quoted by James in Acts 15 when the Jews discussed the inclusion of the Gentiles;

Amo 9:13 "Behold, the days are coming," declares the LORD, "when the plowman shall overtake the reaper and the treader of grapes him who sows the seed; the mountains shall drip sweet wine, and all the hills shall flow with it. 14 I will restore the fortunes of my people Israel, and they shall rebuild the ruined cities and inhabit them; they shall plant vineyards and drink their wine, and they shall make gardens and eat their fruit. (James quoted Amos 9:11‐12 in Acts 15:16‐17.)

Here is another passage from Isaiah 49, which Paul quoted in Acts 13 as his authority to turn to the Gentiles.

Isa 49:5 And now, says Jehovah who formed Me from the womb to be His servant, to bring Jacob again to Him, Though Israel is not gathered, yet I shall be glorious in the eyes of Jehovah, and My God shall be My strength. 6 And He said, It is but a little thing that You should be My servant to raise up the tribes of Jacob, and to bring back the preserved ones of Israel; I will also give You for a light to the nations [the Gentiles], to be My salvation to the end of the earth. 7 So says Jehovah, the Redeemer of Israel, His Holy One, to Him whom man despises, to Him whom the nation hates, the servant of rulers: Kings shall see and arise, rulers also shall worship, because of Jehovah who is faithful, the Holy One of Israel, and He shall choose You.

Paul quoted Isaiah 49:6 in Acts 13:47. How could Paul’s turning to the Gentiles in Acts 13 be seen as the introduction of our present calling of the Gentile “body of Christ” when Isaiah says it was a time of Israel’s rising and restoration?

8. The salvation of the Gentiles during Acts … was in a time when God was still being faithful to Israel. When Paul wrote to the Romans, he declared that the “gifts and calling of God” were without change of mind, Roms.11:29. God’s faithfulness to Israel was not dependent on their belief in and acceptance of the Lord as their Messiah and Saviour. All Israel will be saved was Paul’s confident affirmation in Roms.11:25‐26. Paul wasn’t being two faced or hiding truth from those readers when he said God had not changed his mind regarding Israel.

Rom 3:3 For what if some did not believe? Surely their unbelief will not nullify the faithfulness of God? Rom 3:4 Certainly not!

Gentiles were being saved in a time when God was faithfully holding out His hands to His people, ready to send Christ back to them as promised through Peter in Acts 3:17‐20. The imminent return of Messiah/ Christ, the hope of Israel, was the hope of the Acts period. Roms.113:11‐12, 15:4‐13 and 16:20.

Conclusion: The salvation of the Gentiles during the Acts period must not be seen as “evidence” that the Lord had started something new. Our tradition that the book of Acts records the history of the early “church” must be discarded for the confusion it is. Our tradition that the Acts was a transition period during which Paul was gradually given truth for today must also be discarded as scripturally baseless.

The Acts period was an extended opportunity for the nation of Israel to respond to the grace of God and acknowledge Jesus of Nazareth as their Messiah. The book of Acts covers approximately 40 years, a period of probation, and at the end of the book the final appeal is given to the dispersed Israelites in Rome. They, like so many before them, argued about the truth and Paul was inspired to pronounce the judgmental prophecy of Isaiah 6 against the nation. Israel was set aside, God’s purposes for her postponed. Then the salvation of God was sent to the Gentiles without Israel and the terms and conditions of today’s dispensation were given to one man, Paul.

Today we praise God for the Post-Acts ministry of Paul. May we all rejoice in today’s riches of grace where Jew and Gentile have been created as “one new man.” Where our inheritance has nothing to do with the promises made to Israel’s fathers, our in heritance and hope cannot be found in prophecy.

From: https://bibleunderstanding.com/salvation-of-the-gentiles-during-the-acts-period/