What freedom is Paul talking about? He is talking about freedom from this present age and freedom for life in the new creation inaugurated by Christ, freedom from a life centred on oneself to a life centred on Christ. The contrast is between the flesh and the Spirit, between following one’s own guidance and being directed by God’s Spirit, between being selfish and acting in selfless and outgoing love. He clearly doesn’t mean freedom from all obligations because he goes on to urge his readers to perform the duties of a slave for one another.
We are in a new realm of existence in which the Holy Spirit sensitises us to what is contrary to God’s will, gives us a standard of values which does not govern us from the outside but from within, and enables us to do what benefits others (cf. Longenecker).
“A Christian is the most free lord of all, and subject to none; a Christian is the most dutiful servant of all, and subject to everyone.” (Martin Luther)