Good Advice – or Depriving Someone of Business?


Reuven sees his friend, Shimon, about to buy a food mixer in Levi’s Appliances
store. He knows that the same model is available at a much cheaper price down the street.
Is he permitted to go in and warn Shimon that he is about to waste his money? Would there
be any difference if he himself were to be the owner of the other shop?


In Bovo Basro (21b), Rabboh says that a fisherman may not cast his net within a
"parsoh" (about 4 km) of another fisherman’s net. The reason for
having to keep such a big distance is that the fish have already spotted the bait in the
first fisherman’s net from a distance and he is therefore sure of catching these
fish. One who sets up a rival net is therefore considered to be damaging another
person’s livelihood (Rashi). Despite the fact that (a) the fish in the sea are
free for all and (b) that these fish have not yet been caught in the first
fisherman’s net, the expected result of the casting of his net render them as if they
were his. Tosafos add (Gittin 60b and Kiddushin 59a) that if fishing
is the first person’s livelihood, one who interferes with his net is considered to
have infringed the Torah prohibition of stealing (if it is not, the prohibition is

According to the Chasam Sofer (Responsa to Choshen Mishpot, No. 79), we
derive a principle from this case. Whenever a trader performs some act in order to attract
a customer and the parties have already reached agreement about the conditions of sale, it
becomes forbidden at that stage for any other trader to persuade this customer to do
business with him (or to buy elsewhere). The reason for this law is that the first trader
is considered to have already "acquired" this customer, just as the first
fisherman is considered to have already acquired the fish in the vicinity of his net. In
reality, the two cases are not exactly the same. The potential customer can back out of
the deal, even though he has reached basic agreement with the vendor. However, once the
fish has seen the bait, its nature will not allow it to change its plans!

The Bach (to Tur, Choshen Mishpot 237) goes even further. Let us suppose that
buyer and seller are still at the bargaining stage. The buyer names a low price, the
seller a high one. At this stage, another trader intervenes and offers to sell the same
item for a price that is even lower than that bid by the buyer. The intervening trader is
deemed to have acted incorrectly, even though his offer would have saved the buyer a large
sum of money. The Bach explains that when buyer and seller are negotiating about the
price, even though there seems to be a wide gulf between them now, in all probability they
will eventually come to agreement somewhere in the middle. The third party’s
intervention is therefore deemed to have ruined a deal that was expected to come to
fruition. Thus, his behavior is considered incorrect.

Our discussion is limited to cases where the higher price being charged by the first
trader is still within the permitted range. However, if he is overcharging (see MDbusiness
"Overcharging and Underpaying" in this series for definitions), one should warn
the potential victim of the trap waiting for him. One should act in this way even if the
result will be that he buys from you and you thus benefit from the additional business.

THEREFORE, Shimon should not intervene unless the price Reuven is being charged
exceeds the limit for overcharging. Once the shopkeeper has managed to gain Reuven’s
basic agreement to the deal, this deal is deemed to be already concluded. Another
application of the same principle would be a taxi company starting out in business. It
would be forbidden for them to actively persuade existing customers of another taxi
company to transfer their custom.

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