In "Word Focus" Glenn McClure writes:
First, the spirit of bondage — the Greek word for bondage refers to one who is under unwilling and unhappy servitude. It is one who is in subjection to a master, whether that master is a person, a passion, or an influence… On the other hand, the awareness of the new relationship is the Spirit of adoption. The word adoption means “placing as a son.” It is taking and treating a stranger as one's own child. Instead of fear, as in the slave-master relationship, there is the feeling of love, affection, and confidence which pertains to children. This spirit of adoption is diametrically opposed to the spirit of bondage.
Source: Studies in Romans: Adult Teacher's Insights, page 40.