1 Corinthians 1:17

Context
1:17 For Christ did not send me to baptize, but to preach the gospel – and not with clever speech, so that the cross of Christ would not become useless. ¹ 

1 Corinthians 2:8

Context
2:8 None of the rulers of this age understood it. If they had known it, they would not have crucified the Lord of glory.

1 Corinthians 9:16

Context
9:16 For if I preach the gospel, I have no reason for boasting, because I am compelled to do this. Woe to me if I do not preach the gospel!

1 Corinthians 9:27

Context
9:27 Instead I subdue my body and make it my slave, so that after preaching to others I myself will not be disqualified.