2 Even if I am not an apostle to others, to you at least I am; for you are the seal of my apostleship in the Lord.
1 Corinthians 9:2 Cross References - MNT
John 6:27
27 "Labor not for food which perishes, but for the food that endures eternal life—that which the Son of man will give you; for on the Father—God—has set his seal."
2 Corinthians 3:1-3
1 Am I beginning again to "recommend" myself? Or do I need, as some do, letters of commendation either to you or from you?
2 You are my letter, written on my heart, known and read by all men.
3 Since all can see that you are a letter of Christ transcribed by men, written not with ink, but with the Spirit of the living God, not on tablets of stone, but on human hearts as tablets.
2 Corinthians 12:12
12 In truth the signs of the true apostle were wrought among you in all patience by signs and marvels and powers.