John Calvin Commentary 1 Corinthians 7:21

"Wast thou called being a bondservant? Care not for it: nay, even if thou canst become free, use [it] rather." — 1 Corinthians 7:21 (ASV)

Art thou called being a servant? We see here that Paul’s purpose is to reassure their consciences, for he exhorts servants to be of good cheer and not be discouraged, as if servitude were a hindrance to their serving God. Care not for it then; that is to say, do not be concerned about how you might throw off the yoke, as if it were a condition unsuitable for a Christian, but be content in your mind. And from this we infer, not merely that it is due to the providence of God that there are different ranks and positions in the world, but also, that respect for them is commanded by His word.

But if thou mayest even be made free. The word even (in my opinion) simply has this force — “If, instead of servitude, you could attain even liberty, it would be more beneficial for you.” It is uncertain, however, whether he continues to address servants, or turns to address those who are free.

In the latter case, γενέσθαι would here mean simply to be. Either meaning fits sufficiently well, and they amount to the same thing. He means to suggest that liberty is not merely good, but also more beneficial than servitude. If he is speaking to servants, his meaning will be this — While I exhort you to be free from anxiety, I do not prevent you from even taking advantage of liberty, if an opportunity arises for you.

If he is addressing those who are free, it will be a kind of concession, as if he had said — I exhort servants to be of good courage, although a state of freedom is preferable, and more to be desired, if one has the choice.