Our parasha deals primarily with Yitzchak, the son or Avraham and Sarah, whose education was at the top of Sarah’s interest. Many parents, in fact, leave no stone unturned to ensure that their children have excellent educations. They pay for good schools, look for a good atmosphere, and try to protect them from dangers of all sorts. For better or for worse, though, the most important factor in their success is the personal example the parents set.
The gemara (Nedarim 20b) teaches us that one can impact his children even before they are conceived, going through nine improper behaviors that can leave the resulting offspring spiritually blemished. The major theme is that the parents’ relations must take place within a spirit of trust, ethics, and proper regard towards one’s partner. The Shulchan Aruch (Even Haezer 25:8-9) rules that it is forbidden to have relations while withholding one’s plans to get divorced or to be drunk during relations. The idea is simple. A joint life is based on trust, mutual respect, and unparalleled closeness. Someone who hides his intention to divorce and goes on in this regard as if nothing is wrong, breaks the basic trust which is at the heart of the whole relationship.
Let us bring an example of the above from Tanach. Shmuel I:25 deals with a severe dispute between David and Naval as to what makes one king. Avigail was Naval’s wife, and the navi refers to her as "of good intellect." Chazal count her as one of the seven prophetesses (Megilla 14a) and a tzadeket (Mishna, Sanhedrin 2:4), and she taught David, her future husband, a lesson about the halachot of kingship. Despite her greatness, she did not merit being the mother of the Davidic dynasty of kings. Not only was her son not appointed to succeed David, but she is referred to as "the wife of Naval Hacarmeli" (Shmuel I:30:5) even after Naval’s death and her marriage to David. Why does she receive this treatment?
The gemara says that her prophecy was that David would be king after the deaths of Shaul and her husband, on condition that David would not seize the throne by force. After informing David all these things, she tried to ensure a role as queen by hinting to David that he should marry her after her husband died (Shmuel I, 25:31), as David seemed to understand and accept (ibid. 35). The gemara (Bava Kama 92b) metaphorically identified Avigail’s intention in her veiled speech. The navi continues that when Avigail returned home from meeting David, she found Naval drunk, and the language applies that they had relations (compare ibid. 36 to Bereishit 16:4, 29:23, & 29:30). This was inappropriate on several grounds, including that he was drunk and that she was planning to marry David. Therefore, this otherwise great woman was punished in that her marriage to David never reached its potential – she was still known as Naval’s wife and did not merit being the mother of royalty. This story can thus be a source for the gemara’s stress of proper mindsets and behavior when involved in intimacy.
May we all merit having offspring who find favor in the eyes of Hashem and man, which, we have seen, is aided when the parents have the proper relationship based on ethics and trustworthiness.