It is implied that Christ has set believers free from the old covenant. Here freedom from the old covenant is a metaphor for not being obligated to obey it. Alternate translation: "You were called to freedom from the old covenant" or "Christ has chosen you to not be obligated to the old covenant" (See: [[rc://en/ta/man/jit/figs-metaphor]])
The word "flesh" here is a metonym for people's sinful nature. The relationship between the opportunity and the sinful nature can be stated more clearly. Alternate translation: "an opportunity for you to behave according to your sinful nature" (See: [[rc://en/ta/man/jit/figs-metonymy]] and [[rc://en/ta/man/jit/figs-explicit]])