What is the sin of St.Peter that made St.Paul opposed him in Galatians2:11?

What is the sin of St.Peter that made St.Paul opposed him in Galatians2:11?

Answer

St.Peter did not commit any sin in Galatians2:11 and St.Paul based his opposition with Peter on the Doctrine agreed upon at the Council of Jerusalem.

St.Peter agreed with St.Paul inspiration how to preach the Gospel of Christ to the Gentiles by not requiring them to follow the Mosaic Law or restrictions like circumcission and other known Jewish Law but since the Council of Jerusalem was not yet fully understood and embraced by other Jews like some of the Disciples of St.James present in Antioch, St.Peter prudently withdraw from eating with the Gentiles the moment he sense some disapproval with Jews present and perhaps with the intention to explain His side and explain the Doctrines agreed upon with the Council of Jerusalem with St.Paul.

But, St.Paul obviously filled with the Holy Spirit was inspired to use the incedent to convict the heart of the Jews including St.Peter that although Jesus did not come to abolished the Mosaic Law but "Unity and Brotherhood" is above all the desired by Jesus in the Gospel. Jesus Christ clearly teaches in His public ministry that the greatest of all this is not the perfection of faith but Love. Faith must be express in love and thru charity as Jews and Gentiles are all adoptive children of God. St. Paul obviously was inspired by the Holy Spirit to remind St.James disciples and all the Jews present of the need for them to expressed the faith with charity towards unity with the Gentiles.

"And now these three remain: faith, hope, and love; but the greatest of these is love."(1Corinthian13:13)

"For in Christ Jesus neither circumcision nor uncircumcision has any value. All that matters is faith, expressed through love.(Galatians5:6)

We need also to consider that the Council of Jerusalem is not yet clear to all the Jews and St.Peter in Antioch were showing St.Paul that he believed in the inspiration to Him by Jesus on how to treat the converted Gentiles, and so St.Peter conversing, associating and eating together with the converted Gentiles had proved that he followed that inspiration and their agreement.

Below is some explanations of the incident citing Barnabas as the key person that facilitate the meeting St.Paul and St.Peter and the other Apostles in the year around AD47 to AD51.

Barnabas and Paul had been "for no small time" at Antioch, when they were threatened with the undoing of their work and the stopping of its further progress. Preachers came from Jerusalem with the gospel that circumcision was necessary for salvation, even for the Gentiles. The Apostles of the Gentiles, perceiving at once that this doctrine would be fatal to their work, went up to Jerusalem to combat it; the older Apostles received them kindly and at what is called the Council of Jerusalem (dated variously from A.D. 47 to 51) granted a decision in their favour as well as a hearty commendation of their work (Acts 14:27-15:30). On their return to Antioch, they resumed their preaching for a short time. St. Peter came down and associated freely there with the Gentiles, eating with them. This displeased some disciples of James; in their opinion, Peter's act was unlawful, as against the Mosaic law. Upon their remonstrances, Peter yielded apparently through fear of displeasing them, and refused to eat any longer with the Gentiles. Barnabas followed his example. Paul considered that they "walked not uprightly according to the truth of the gospel" and upbraided them before the whole church (Galatians 2:11-15). Paul seems to have carried his point. Shortly afterwards, he and Barnabas decided to revisit their missions. Barnabas wished to take John Mark along once more, but on account of the previous defection Paul objected. A sharp contention ensuing, the Apostles agreed to separate. Paul was probably somewhat influenced by the attitude recently taken by Barnabas, which might prove a prejudice to their work. Barnabas sailed with John Mark to Cyprus, while Paul took Silas an revisited the churches of Asia Minor. It is believed by some that the church of Antioch, by its God-speed to Paul, showed its approval of his attitude; this inference, however, is not certain (Acts 15:35-41).

https://www.ewtn.com/saintsholy/saints/B/stbarnabas.asp

Below is some exceprt from Fr.Erchert answered on EWTN site; explaining that St.Peter had not committed a sin but his behaviour out of fear and pressure from the Jews who had not yet understand the Holy Spirit inspiration to St.Paul as agreed upon at the Council of Jerusalem contributed to the confusions. And since the Holy Spirit wanted to clear out the confusions that had developed corrected the Jews infront of the Gentiles to prevent future incedent to happen and St.Paul was the one inspired to do the rebuked. The rebuked is not directly intended to St.Peter but to the Jews particularly to the Disciple of St.James as the Holy Spirit knows our heart. St.Peter did not commit a sin but his error is he lacked courage to expressed with conviction his belief on the agreed doctrine at the Council of Jerusalem.

Verse nine concludes the account of a Council at Jerusalem which included Peter at which the apostles approved of the Gospel to the Gentiles without circumcision and the bulk of Mosaic restrictions. Yet subsequent to this, because of peer pressure, Peter drew back from taking meals with the Gentile Christians. This pressure was, no doubt, from Jewish Christians who held tightly to the distinctions between clean and unclean. At any rate, in light of his character as evident in the Gospels, in one sense it is no surprise that Peter acted in such a manner out of fear; for even though the Holy Spirit was active in this leader of the apostles, he was still human and subject to human frailty, especially with regards to personal weaknesses.

But as to the issue of infallibility, this is not claimed to be with regards to everything that a pope says or does, but in those matters in which he intends to speak infallibly, specifically, in matters of faith and morals. A pope may behave badly or choose poorly, for there is no such immunity from human weakness in every aspect of his life. In the case of St. Peter, he may not have sinned by his action but did not act courageously as he might have. And St. Paul challenged the behavior, given the implications to the Gospel of the behavior of Peter. In other words, only because there was so much at stake did the Apostle to the Gentiles challenge publicly the Vicar of Christ. But I would not suggest such public reproofs to a pope today, unless you have been called by God to the level of St. Paul. Even so, you had better be sure of your position, as St. Paul was of his.

http://www.ewtn.com/v/experts/showmessage.asp?number=359156&Pg=&Pgnu=&recnu=

In closing, we can see that St.Peter did not sinned but only lack the courage to upheld with conviction what they had agreed upon at the Council of Jerusalem.

It is true that they didn’t have the NT so what was the issue? Hypocrisy

'There shall be one standard for you; it shall be for the stranger as well as the native, for I am the LORD your God.'" Leviticus 24:22

Peter was setting up division in the body of Christ between the Jew and the Gentiles. But no one enters by blood rights into the body of Christ according to John1:13

who were born, not of blood nor of the will of the flesh nor of the will of man, but of God

Therefore if all men enter by the will of God there should not have been an issue for Peter to have remained at the table with the gentiles.

User SLM comment added to the answer

“The apostles and the elders were gathered together to consider this matter. And after there had been much debate, Peter stood up and said to them, "Brothers, you know that in the early days God made a choice among you, that by my mouth the Gentiles should hear the word of the gospel and believe. And God, who knows the heart, bore witness to them, by giving them the Holy Spirit just as he did to us, and he made no distinction between us and them, having cleansed their hearts by faith.” ‭‭Acts‬ ‭15:6-9‬ ‭ESV‬‬

Apostle Paul was in the audience

“And all the assembly fell silent, and they listened to Barnabas and Paul as they related what signs and wonders God had done through them among the Gentiles.” ‭‭Acts‬ ‭15:12‬ ‭ESV‬

It would be hypocritical of Peter to acknowledge the Gentiles (Ten Lost tribes of Israel and gentiles) as being indistinct from the Jews (Tribe of Judah and Benjamin only) if both are accepted into the body and receive the same Holy Spirit by faith.

It could be that Paul is pointing out Peter’s inconsistency or hypocrisy

The basis was the revelation of Jesus Christ.

11 But I certify you, brethren, that the gospel which was preached of me is not after man.

12 For I neither received it of man, neither was I taught it, but by the revelation of Jesus Christ. (Galatians 1:11-12)

Paul testified that he was "an apostle, (not of men, neither by man, but by Jesus Christ" (Galatians 1:1). Therefore, we do not have to be physically studying beside Jesus to be taught by Him. Through the Holy Spirit and even Jesus through visions, Paul was given special revelations.

Also, although the twelve disciples studied beside Jesus, they didn't understand many things until after Jesus died. When they truly searched, the Holy Spirit gave them understanding of the scriptures concerning Jesus' ministry and death. In fact, Peter had to repent greatly, because he had relied on his own righteousness instead of God, and ended up denying Jesus three times.

In this case, Peter had actually understood and believed in the same truth as Paul. We know this because God had impressed the point into Peter by giving him the special vision with the unclean animals.

"What God hath cleansed, that call not thou common." Acts 10:15

After this, Peter personally was sent to Cornelius' house to baptize them and to witness the Holy Spirit descending on them. Later, he testified to the Jerusalem Christians about this as a sign of God's acceptance of the gentiles. Therefore, if God had accepted them as His adopted sons, who are the Jews to refuse eating with them?

34 Then Peter opened his mouth, and said, Of a truth I perceive that God is no respecter of persons:

35 But in every nation he that feareth him, and worketh righteousness, is accepted with him. (Act 10:34-35)

Therefore, it was extremely hypocritical for Peter to then allow peer pressure and habits to influence him. As a leader, his action of not eating with the gentiles was an offence to the gospel. It was leading people to the wrong direction. Therefore, Paul had to rebuke him publicly.