For though I am free from all men, I have made myself a slave to all, so that I may win more. (1 Cor 9:19)
“Finally, the apostle spells out his overall posture and the particular line he adopts, as a concrete expression of that stance, in the different social settings. Of cardinal importance is his opening statement where he uses language of servanthood to refer to his overall stance: Paul makes himself a slave … to everyone for the purpose of winning as many as possible (v. 19). This language is highly significant and assumes a prominent role within Paul’s argument in these chapters (8:1-11:1) ….
For Paul Jesus is the supreme example of humble, self-sacrificing, self-giving service. He emptied himself by taking ‘the form of a slave’ … and humbled himself by becoming obedient to the utmost limit, death on a cross. Jesus is … the paradigm of servanthood and of true Christian ministry. The apostle regularly uses servant language to describe his own ministry (douloi, 2 Cor 4:5) and to express believers’ relationships with one another (douleuete, Gal 5:13). The radical nature of these expressions can hardly be overestimated. Slavery in contemporary society pointed to the extreme deprivation of one’s rights, including those relating to one’s own life and person. When Jesus emptied himself by embracing the divine vocation and becoming incarnate he became a slave, without any rights whatever (Phil 2:7). …
As one who was ‘free’ but who voluntarily made himself a slave, Paul was living in conformity with the example of his Lord and thus showing a truly Christian life-style. The Corinthians had believed that their apostle was second-rate (vv. 15-18) and that he was guilty of vacillating and inconsistent behavior. They could not have been further from the truth, for he had willingly renounced his rights and put himself at the disposal of others. Later he will call upon them to follow his example as he follows the pattern of Christ (11:1).” (O’ Brien, P. T. Gospel and Mission in the Writings of Paul, 100-101.)