agorazō

This is the everyday word for buying, drawn straight from ordinary life. It comes from the word for the marketplace, the open square where people traded, so at its root it means to do business there: to hand over money and take away goods.

The New Testament uses it for all sorts of purchases. People buy food when a crowd needs feeding, buy a field or a pearl of great value, buy oil for their lamps, buy spices to prepare a body for burial, and go on buying and selling as usual right up to the day judgment falls. In every case the picture is the same plain transaction: a price is paid and something changes hands.

Because it is such a common word, its force in any verse comes mostly from what is being bought and why, not from the word itself. It carries no special religious weight on its own, which is exactly what makes its second, deeper use so striking.

A handful of passages take this ordinary marketplace word and lift it into the language of rescue. Believers are said to have been bought, and the price named is not money but the blood of Christ. The image is deliberate and shocking: people who belonged to sin and death are purchased and so become the possession of the one who paid for them.

Paul presses this on his readers as a claim on how they live. Because they were bought at such a cost, their bodies and their whole selves are no longer their own to do with as they please. The book of Revelation sings the same note in worship: the slain Lamb purchased people for God from every tribe and nation. In these places the word keeps its plain sense of paying a price to acquire something, but the thing acquired is human beings and the buyer is God.

This is close to the idea of ransom, the payment that frees a captive, though this word leaves the emphasis on the new ownership that results rather than on the release itself. It is the reason the New Testament can call believers slaves of Christ in a way meant as good news: they have simply changed owners, from a cruel master to a loving one.