1 Corinthians 9:2

If I am not an apostle to others, yet doubtless I am to you. For you are the seal of my apostleship in the Lord.

Surrounding context

9:1 Am I not an apostle? Am I not free? Have I not seen Jesus Christ our Lord? Are you not my work in the Lord?

9:2 If I am not an apostle to others, yet doubtless I am to you. For you are the seal of my apostleship in the Lord.

9:3 My defense to those who examine me is this: