'Selling' in the Bible

Jacob said, “Swear [an oath] to me today [that you are selling it to me for this food]”; so he swore [an oath] to him, and sold him his birthright.

If the years [until the next Jubilee] are many, you shall increase the price, but if the years remaining are few, you shall reduce the price, because it is the number of crops that he is selling to you.

Differing weights [one for buying and another for selling] and differing measures,Both of them are detestable and offensive to the Lord.