Paul cannot boast about his work of proclaiming the gospel, because it is a duty that Christ has laid on him (see Acts 9:6 Acts 9:15; Acts 22:21; Acts 26:15–20; Romans 1:5; Galatians 1:15–16; 1 Thessalonians 2:4). If he was to neglect this duty, he could only expect divine punishment (Woe to me...!
).
16 For if I preach the gospel, that gives me no ground for boasting. For necessity is laid upon me. Woe to me if I do not preach the gospel!