Heidegger's Bible Handbook: 1 Peter: Occasion of the Epistle
3. The Occasion of the Epistle.
Saint Augustine, libro de fide et operibus, chapter 14, thinks that the occasion of writing, as for John, James, and Jude, so also for Peter, was provided by the erroneous opinion of those that preached that a faith without works was sufficient for salvation. Moreover, it appears to be evident from the very argument of the Epistle, and from the state of the Church in those times, and also from the end on account of which Saint Paul went up to Jerusalem to Peter and James, Galatians 1:18, 19; 2:2, that there were those that doubted of the agreement of Peter, Paul, and Silas or Silvanus. Therefore, he thought it necessary to testify to his own consent in the doctrine of faith, and to confirm the Hebrews in the faith received, and to imbue them in holiness of life.