PROHIBITED WAYS OF DECEPTION (Yerushalmi Halachah 3 Daf 3b)
תני לא (ישלח)[יפתח] לו חביות מכורות לחנווני מפני שהוא כטוענו טענת חנם
Beraisa: A host should not open barrels sold to a shopkeeper because he is fooling the guest into thinking that he is suffering a great financial loss for the sake of the guest by wasting the rest of the wine, when really there is no loss, as he will immediately give them to the shopkeeper.
לא יסרב אדם בחבירו לארחו בשעה שאינו רוצה
A person should not overly urge someone to eat with him when he knows that the guest does not want to come (as he is deceiving the guest that he wants him to come, when that is really not the case).
לא ירבה לו בתקרובת בשעה שהוא יודע שאינו מבקש.
A person should not persistently try to give gifts to someone when he knows that he will not accept them (as he is doing this merely to deceive the person that he is try to be generous with him).
Question: In what way may a person not try to give gifts?
[ידע שהוא רחוץ](בזווי אוחרי) [והוא מטרח עלוי].
Answer: When he is sure that the person will not accept even if he persists.
ובירושלם היה הופך [דף ד עמוד א] (עיכליה)[פילכיך] דימינא לשמאלא.
In Yerushalayim, when they wanted to show friendship, rather than giving gifts, a person would transfer the head covering that his friend was holding from his right hand to his left hand.