Ketubot 70A

רבי מאיר היא, דאמר: מצוה לקיים דברי המת.

It is in accordance with the opinion of R' Meir, who says it is a mitzva to fulfill the instructions of the dead, as the Mishnah states that the third party must fulfill the instructions of the deceased, although the daughter is likely to do as she pleases after the third party fulfills his part. In this manner, Ilfa successfully answered the man’s challenge.

אמר רב חסדא אמר מר עוקבא, הלכתא: בין שאמר ״תנו״ ובין שאמר ״אל תתנו״⁠ — נותנין להם כל צורכם. הא קיימא לן הלכה כרבי מאיר, דאמר: מצוה לקיים דברי המת? הני מילי במילי אחרניתא, אבל בהא מינח ניחא ליה, והא דאמר הכי ⁠— לזרוזינהו הוא דאתא.

Rav Ḥisda said that Mar Ukva said: The halakha is that whether he says: Give a shekel or whether he says: Do not give more than a shekel, the court gives the sons enough for all of their needs. The Talmud asks: But how could we disregard the father’s words and give more, when the father said to give only a shekel? We maintain that the halakha is in accordance with the opinion of R' Meir, who says that it is a mitzva to fulfill the statements of the dead. How, then, may the father’s instructions be ignored? The Talmud answers: This principle applies only in other matters, in which there is a mitzva to fulfill his wishes, but in this instance it is certainly preferable to him that his children be appropriately provided for. And the reason that he said this statement limiting the allowance is that he came to encourage them to adopt thrifty spending habits.

תנן התם: הפעוטות מקחן מקח וממכרן מכר במטלטלים.

We learned in a Mishnah there (Gittin 59a): With regard to children, their acquisitions are considered acquisitions and their sales are considered sales. This is the case with respect to movable properties, but not with respect to real estate.