If I be not an apostle unto others, yet doubtless I am to you: for the seal of my apostleship are you in the Lord.
All Commentaries on 1 Corinthians 9:2 Go To 1 Corinthians 9
Ambrosiaster
AD 400
Those Jewish believers who nevertheless continued to observe the law of Moses denied that Paul was an apostle because he taught that it was no longer necessary to be circumcised or to observe the sabbath. Even the other apostles thought that he was teaching something different because of this, and they denied that he was an apostle. But to the Corinthians Paul was an apostle, because they had seen the signs of God’s power in him. Commentary on Paul’s Epistles.