Genesis: 28:9 – So Esau went to Ishmael, and he took Mahalath, the daughter of Ishmael, the son of Abraham, the sister of Nebaioth, in addition to his other wives as a wife.
Babylonian Talmud – Megila 17a: From the fact that the verse mentions that Mahalath was the daughter of Ishmael, we already know that she was the sister of Nebaioth. What is the purpose of telling us this fact that is already known? To teach us that immediately after Ishmael betrothed her to Esau, he died. It was then Nebaiot who completed the marriage process [in Ishmael’s place].
Torah Temimah Colloquial Translation on Note #4
Look at Rashi’s commentary on this verse as it pertains to the above quoted Gemora.
Also note that Rabbi Yosef Karo in Section 167 and also cited by the Ramah in Yoreh Deah (section 140) in the laws of honoring one’s parents that in matter of marriage, the duty of honoring one’s parents does not apply. That is to say, if the father is pushing his son not to marry a specific woman, the son is not obligated to obey him. See also the Vilna Gaon’s comments on this issue.
If this is so, this entire Torah section requires further explanation. How could Yitzchak then command Yaacov to not marry a wife from the daughters of Canaan? (Genesis 28:1) If the law is that Yitzchak does not have the ability to command his son in this matter, how could he command Yaacov? Perhaps he could have used the phrase “request” but certainly not the phrase “command” as was actually the case.
Perhaps there is room to say that if a father commands his entire household not to marry into a certain family (as was the case with Yitzchak) then he would have authority. We find similarly in the Gemorah in a variety of issues that the children of a family can be pressured not to change the custom of their family. In this case, here, the family of our forefathers were commanded not to marry from the daughters of Canaan. As Abraham said to Eliezar (Genesis 24:3) “don’t choose a wife for my son from the daughters of Canaan”. As the Gemora in Pesachim states, Abraham was warning Eliezar regarding Yitzchak not to select a wife from the daughters of Canaan. Thus, it is clear that there was a tradition [in their family]. This is the reason why Yitzchak had authority to command Yaacov regarding his family custom/tradition.
It is a wonder that no halachic authorities have pondered this question [in terms of its ramifications for our time].
Translator’s Note: It seems clear that the inference from the Torah Temimah’s note is that, as a rule for our times, parents do not have the authority to dictate to their children who they can or cannot marry.