Writing a Will
The Rabbis interpret a will as an elaborate gift, making it permissible within Jewish law.
Reprinted from The Jewish Religion: A Companion, published by Oxford University Press.
The chief religious problem with regard to a will, in which a person declares how his estate is to be distributed after his death, is that, on the face of it, any disposition that is not in accord with the laws of succession, as stated in the Torah (Numbers 27:8-11; Deuteronomy 21:16-17), is contrary to the laws of the Torah. According to the Talmudic sources, however, the laws of succession only apply where the testator states that the deposition of his property in is the form of an inheritance. The laws of succession do not apply if the deposition is given as a gift, that is, if the estate is distributed while the man is still alive, with the stipulation taking place immediately but the distribution only when he dies, since a man is allowed to give away that which he owns to whomsoever he pleases.
The key passage in this connection is the Mishnah (Bava Batra 8:5) which states: 'If a person gives his estate, in writing, to strangers, and leaves out his children, his arrangements are legally valid (literally, what he has done is done), but the spirit of the Sages finds no delight in him. Rabban Simeon ben Gamaliel said: If his children did not conduct themselves in a proper manner he will be remembered for good.'
Most authorities, consequently, see no harm in a man making a will in favor of whomsoever he wishes, provided it is in the form of a gift not an inheritance, since the will is precisely that--a gift given in his lifetime to come into operation 'from now until after his death,' as this is formulated in the Mishnah in the same tractate.
Nevertheless, he should leave a substantial amount to his children in order to satisfy the 'spirit of the Sages.'