Tradition
St. Clement of Alexandria
Fragments
Chapter 22
Eusebius: Ecclesiastical History, Book. VII. II. 1.
To James the Just, and John and Peter, the Lord after His resurrection imparted knowledge (τὴν γνῶσιν.) These imparted it to the rest of the apostles, and the rest of the apostles to the Seventy, of whom Barnabas was one.
Source: Fragments (New Advent)