'Buy' in the Bible

I counsel thee to buy of me gold purified by fire, that thou mayest be rich; and white garments, that thou mayest be clothed, and that the shame of thy nakedness may not be made manifest; and eye-salve to anoint thine eyes, that thou mayest see.

and that no one should be able to buy or sell save he that had the mark, the name of the beast, or the number of its name.