Responsa על כתובות 191:20

Q. A widow seized for her sustenance all the money left by her late husband. The orphans claim that she thus seized more than the value of her ketubah. May she be compelled to return the money?
A. Although R. Isaac b. Abraham believes that the talmudic ruling, "a widow who seized (her husband's) valuables for her sustenance may retain such valuables (Ket. 96a)," applies to cases where it is known that the widow seized less than the value of her ketubah; his brother, R. Samson b. Abraham, and Maimonides, believe that the ruling applies to any amount seized by the widow, for the amount a widow may need for her sustenance is indeterminate. Therefore, the widow may retain the money she has seized for her sustenance. She need take no oath as to the amount seized, since such oath would serve no purpose. However, should she subsequently demand additional funds for her sustenance, she would have to take an oath as to the amount she seized and to the manner she used it. She may restrain the orphans from selling immovables they inherited from her late husband since her sustenance is a lien upon such property, but she can not invalidate a sale already concluded.
SOURCES: L. 394; Am II, 3; Mord. Ket. 251; Tesh. Maim. to Nashim, 27; Asheri Ket. 11, 3. Cf. Cr. 129b.

Q - A married a widow L, who brought to A a dowry of valuables worth 500 (?). L had not taken the customary widows oath regarding her ketubah due from her former husband. L died, and the heirs from her former husband demand that A return the valuables to them.
A - Since L did not take an oath regarding her ketubah, A must return all the valuables which he received from L, to the heirs of her former husband.

Q. A widow seized for her sustenance all the money left by her late husband. The orphans claim that she thus seized more than the value of her ketubah. May she be compelled to return the money?
A. Although R. Isaac b. Abraham believes that the talmudic ruling, "a widow who seized (her husband's) valuables for her sustenance may retain such valuables (Ket. 96a)," applies to cases where it is known that the widow seized less than the value of her ketubah; his brother, R. Samson b. Abraham, and Maimonides, believe that the ruling applies to any amount seized by the widow, for the amount a widow may need for her sustenance is indeterminate. Therefore, the widow may retain the money she has seized for her sustenance. She need take no oath as to the amount seized, since such oath would serve no purpose. However, should she subsequently demand additional funds for her sustenance, she would have to take an oath as to the amount she seized and to the manner she used it. She may restrain the orphans from selling immovables they inherited from her late husband since her sustenance is a lien upon such property, but she can not invalidate a sale already concluded.
SOURCES: L. 394; Am II, 3; Mord. Ket. 251; Tesh. Maim. to Nashim, 27; Asheri Ket. 11, 3. Cf. Cr. 129b.