Tertullian — on Gal 1:1 (Against Marcion Book V)

“Should you, however, disapprove of these types, the Acts of the Apostles, at all events, have handed down to me this career of Paul, which you must not refuse to accept. Thence I demonstrate that from a persecutor he became "an apostle, not of men, neither by man; " thence am I led to believe the Apostle himself; thence do I find reason for rejecting your defence of him, and for bearing fearlessly your taunt.”