Swallow the bait Verb + object/complement informal
If you swallow the bait, you take something that someone offers you, or agree to do something that someone asks you to do without knowing that it is a trick or way of getting something from you.
You can't just do whatever he wants you to do. Don't swallow the bait.
The words "buy one, get one free" or "two for the price of one" is applied effectively for sales promotion as many purchasers swallow the bait.
There is no clear information about the origin of this expression; however, a source said that this was an old English phrase and came from in 19th century.
People tend to like forbidden or illegal things just because they are forbidden or illegal.
He must have believed that stolen fruit is the sweetest, and he, therefore, cheated on his partner.