Nedarim 43b (מג:) — the Talmud in English

But if he declared it ownerless before taking his vow -

it is permitted.

And if you say that the object does not leave the possession of the one who declared it ownerless

until it enters the possession of one who acquires it,

then

what difference is there whether he took his vow before declaring it ownerless or declared it ownerless before taking his vow?

Ultimately, the one forbidden by the vow derives benefit from the possession of the one who imposed the vow on him!

He raised this objection against himself, and he answered it himself:

In fact, if the one who declared the object ownerless wishes to retract his declaration, he may do so as long as no one else has acquired it. Nevertheless, if he declared it ownerless before taking his vow, it is permitted for the one forbidden by the vow to use it, because

everyone who takes a vow

does not have in mind something that he has declared ownerless.

Consequently, he did not forbid this object to him at all, even though it is still considered to be in his possession.

Rava raised an objection:

A seriously ill man who had two slaves, and gave

part of

his property

to

the

first slave,

and afterward gave

all [

his property]

to the second,

and that man subsequently recovered from his illness: the

first slave acquired

what his master had given him, and his master cannot retract it, because a gift of part of one’s property is not subject to the law of the gift of a seriously ill person, who can retract it if he recovers from his illness. But the

second slave did not acquire it,

in accordance with the law of the gift of a seriously ill person who gave away all his property, which he may retract if he recovers.

Now, it must necessarily be said that when he gave the second slave the gift, he intended to give him also what he had already given to the first. For if this is not so, but he intended to give him only what remained after what he had given to the first, then he had divided all his property, and this entire gift would be subject to the law of the gift of a seriously ill person; why, then, did the first slave acquire his gift?

Rather, it must necessarily be said that he gave the second slave also what he had already given to the first. We see that he had in mind what he had already given, and the same applies in our case: he had in mind what he had declared ownerless!

Rather, said Rava: This is the reason for Rabbi Yosei’s ruling: It is a decree on account of the gift of Beit Horon

[the incident cited below in the Mishna]. Since it is evident to us that he declared the object ownerless only so that the one forbidden by the vow would acquire it, we are concerned that if we permit this, people will come to permit even a case in which the one who imposed the vow explicitly says that he is declaring the object ownerless so that the one forbidden by the vow will acquire it, as in the gift of Beit Horon.

It was taught in a beraita: One who declares his field ownerless—for all three days

may retract his declaration

even if someone else has already acquired the field. The reason is that the Sages instituted a measure on account of fraudsters: since property declared ownerless is exempt from tithing, they would declare their fields ownerless in order to become exempt, while intending to return and acquire them. It would thus emerge that their declarations of ownerlessness were merely a deception. Therefore, the Sages instituted that this would not constitute ownerlessness at all, and even if someone else acquired the fields, the owners could retract their declarations.

From this point onward,

after three days,

the one who declared the field ownerless

declared it ownerless

may not retract his declaration.

For after three days have passed, there is no longer concern for fraudsters. If he truly intended only to exempt himself from tithing, he would not have waited until after three days to retract his declaration! Rather, certainly he intended a complete declaration of ownerlessness.