Tradition
St. Cyprian
The Epistles of Cyprian
Letter 73
To Pompey, Against the Epistle of Stephen About the Baptism of Heretics.
Argument.— The Purport of This Epistle is Given in St. Augustine's “Contra Donatistas,” Lib. V. Cap. 23. He Says There: “Cyprian, Moreover, Writes to Pompey on the Same Subject, When He Plainly Signifies that Stephen, Who, as We Learn, Was Then a Bishop of the Roman Church, Not Only Did Not Agree with Him on Those Points, But Even Had Written and Charged in Opposition to Him.”
Source: The Epistles of Cyprian (New Advent)