1 Corinthians 9:18

Paul’s reward for preaching the gospel willingly was the privilege of preaching it without cost to his hearers. His highest pay was the privilege of preaching without pay. [Note: Morris, p. 137. See also Barrett, p. 210.] This choice may seem as though it was Paul’s decision rather than a reward from the Lord, but he viewed it as a privilege that came to him from the Lord (cf. 2 Corinthians 11:7-12).

Paul had all the rights of an apostle and was free to insist on them if he chose to do so. He also had the freedom not to insist on them. Relinquishing his right to support corresponds to giving up his right to eat in a pagan temple (1 Corinthians 8:13). In both cases it was the welfare of others that led him to forgo a legitimate right.