Which slavery does the New Testament address?
I quoted a verse from the New Testament, do you need more?
The new testament still predominantly addressed Jewish society, or else cities with a predominantly Greek culture. Christianity was just moving into Roman society during the 1st century. The focus of the NT was not on "this world" but the spiritual world, and how to fit oneself for it. It was not focused on social change; and the emphasis was on the personal, not the political.