I am referring to the ministry to the Gentiles which the nation of Israel found disgusting. They looked upon Gentiles as inferior.
The believers at Jerusalem were taken aback by Peter's visit to Cornelius.
Acts 11
And the apostles and brethren that were in Judaea heard that the Gentiles had also received the word of God.
2 And when Peter was come up to Jerusalem, they that were of the circumcision contended with him,
3 Saying, Thou wentest in to men uncircumcised, and didst eat with them.
4 But Peter rehearsed the matter from the beginning, and expounded it by order unto them, saying,
However, they realized by the fact that they spoke in tongues that
15 And as I began to speak, the Holy Ghost fell on them, as on us at the beginning.
16 Then remembered I the word of the Lord, how that he said, John indeed baptized with water; but ye shall be baptized with the Holy Ghost.
17 Forasmuch then as God gave them the like gift as he did unto us, who believed on the Lord Jesus Christ; what was I, that I could withstand God?
18 When they heard these things, they held their peace, and glorified God, saying, Then hath God also to the Gentiles granted repentance unto life.
What Peter and maybe others started, the apostle Paul and others ran with.
Galatians 2
7 But contrariwise, when they saw that the gospel of the uncircumcision was committed unto me, as the gospel of the circumcision was unto Peter;
8 (For he that wrought effectually in Peter to the apostleship of the circumcision, the same was mighty in me toward the Gentiles
9 And when James, Cephas, and John, who seemed to be pillars, perceived the grace that was given unto me, they gave to me and Barnabas the right hands of fellowship; that we should go unto the heathen, and they unto the circumcision.
The kingdom of God was taught by Paul
Acts 28
23 And when they had appointed him a day, there came many to him into his lodging; to whom he expounded and testified the kingdom of God, persuading them concerning Jesus, both out of the law of Moses, and out of the prophets, from morning till evening.
Preaching the kingdom of God, and teaching those things which concern the Lord Jesus Christ, with all confidence, no man forbidding him.
Romans 14:17
For the kingdom of God is not meat and drink; but righteousness, and peace, and joy in the Holy Ghost.
1 Corinthians 4:20
For the kingdom of God is not in word, but in power.
1 Corinthians 6:9-10
Know ye not that the unrighteous shall not inherit the kingdom of God? Be not deceived: neither fornicators, nor idolaters, nor adulterers, nor effeminate, nor abusers of themselves with mankind,
Nor thieves, nor covetous, nor drunkards, nor revilers, nor extortioners, shall inherit the kingdom of God.
1 Corinthians 15:50
Now this I say, brethren, that flesh and blood cannot inherit the kingdom of God; neither doth corruption inherit incorruption.
Galatians 5:21
Envyings, murders, drunkenness, revellings, and such like: of the which I tell you before, as I have also told you in time past, that they which do such things shall not inherit the kingdom of God.
Colossians 4:11
And Jesus, which is called Justus, who are of the circumcision. These only are my fellowworkers unto the kingdom of God, which have been a comfort unto me.
2 Thessalonians 1:5
Which is a manifest token of the righteous judgment of God, that ye may be counted worthy of the kingdom of God, for which ye also suffer:
What Peter and maybe others started, the apostle Paul and others ran with.
Galatians 2
7 But contrariwise, when they saw that the gospel of the uncircumcision was committed unto me, as the gospel of the circumcision was unto Peter;
8 (For he that wrought effectually in Peter to the apostleship of the circumcision, the same was mighty in me toward the Gentiles
9 And when James, Cephas, and John, who seemed to be pillars, perceived the grace that was given unto me, they gave to me and Barnabas the right hands of fellowship; that we should go unto the heathen, and they unto the circumcision.
Paul did not take what Peter was preaching and "run with it"....look at verse Galatians 2:6 But of these who seemed to be somewhat, (whatsoever they were, it maketh no matter to me: God accepteth no man's person: ) for they who seemed to be somewhat in conference added nothing to me:
Paul received nothing from Peter and the twelve...he did not take what they were preaching and preach it.