ONE who enters a house shall not ask for food, but shall wait until invited. When the goblet is filled, he shall drink it slowly. What is meant by slowly? If it is a cold beverage--in four draughts; if a warm beverage--in three. Said R. Jehudah: This applies to the goblets of Galilee, but as regards the goblets of Judah, which were larger, he may drink it as slow as he pleases. One must not say to his friend: "Come and eat with me, as I did with you," for it gives the impression that he wants to repay with interest. In Jerusalem, however, they invited each other in turn. One shall not send to his friend a barrel of wine with oil on the top thereof, because a serious accident may result from it. It actually happened that one invited his friends to his son's wedding, and when going down to his cellar to get wine, he noticed that the barrel had oil (on the top, and thinking that it was all filled with oil) he hanged himself for shame, and died. Hence the above warning is given.
One should not say to his neighbor, "Take oil from that jug and anoint thyself," knowing that it is empty (even when knowing that the man has no habit of anointing himself), because he puts the man under obligation to him for nothing. The same holds good of food: one should not ask his neighbor to take a meal with him when he knows that he would not do so. One should also not offer presents to his neighbor, knowing that he would not accept them, for the same reason. One should not serve his neighbor with new wine, telling him that it is old wine, because it is equivalent to robbery (if he takes money from him, and even if he does not take money from him he deceives him). For the same reason, when one serves wine to ass-drivers, he shall not say: "Take it away from this one (whom he does not like), and give it to the other one." When one is in the grain-market and has no intention of buying, he should not ask for the prices, for he misleads the sellers.
Sources: Sacred Texts