They likely abused the epistles of the holy Apostle Paul and falsely claimed that there was disagreement in doctrine between these apostles.
Perhaps they had heard, though of course they did not understand, that a certain clash had occurred between them in Antioch (Gal 2:11). Perhaps they misinterpreted it and troubled the believers.
In view of this, the Apostle Peter points to the Apostle Paul, thereby testifying to their mutual unity in doctrine and apostolic activity.
Thus he also confirms believers by this communion and unity between them, the chief apostles. For this reason Peter calls Paul, before the believers, beloved, which is in itself profoundly true, and brother, a fellow disciple and fellow apostle of Christ.
“According to the wisdom given to him”: this is also an indication of the high authority Paul enjoyed among the other apostles of Christ and among the faithful.
Wisdom marked all the teachings and all the actions of all the holy apostles. Yet among them it especially marked the chief apostles Peter and Paul, and the beloved disciple of the Lord, John, so that it is difficult to give precedence to any one of them.
Paul himself testifies of himself that he labored more abundantly than all. This is understood in word, writing, and deed.
“Yet not I,” the humble and wise apostle adds in qualification, “but the grace of God which was with me” (1 Cor 15:10).
“Has written to you”: no doubt this chiefly means Paul’s Epistle to the Hebrews, written especially for Hebrews and Christians from among the Hebrews who lived dispersed in the regions of Asia Minor.
To these regions the Apostle Peter also wrote his epistles (1 Pet. 1:1 and the note; 2 Pet. 2:1 and the note).
No doubt it also means those epistles of Paul written to the Christians of Asia Minor, who were certainly known to them and to the Apostle Peter. Hence the apostle says of Paul: “he has written to you,” namely the epistles to the Galatians, Ephesians, Colossians, and perhaps to Timothy.