Charles Ellicott Commentary Galatians 2:7

"but contrariwise, when they saw that I had been intrusted with the gospel of the uncircumcision, even as Peter with [the gospel] of the circumcision" — Galatians 2:7 (ASV)

Gospel of the uncircumcision—i.e., a gospel for the uncircumcised. The elder Apostles recognized St. Paul because they saw that his teaching was fundamentally the same as their own. At the same time, the success of St. Paul among the Gentiles proved that his mission to them had the divine sanction, just as the success of St. Peter among the Jews specially marked him out as the “Apostle of the circumcision.”

On verses 7-9:

So far from contributing anything new to my stock of doctrine, they were content to confirm and ratify what I taught already.