Parashas Toldos - Who's Really Yitzchok's Father??

There was a couple who were not able to have kids for years. After 10 years they felt it was time to get tested to see what (or who) was the problem. When the man got tested, it turned out he was fine and through process of elimination, they were able to deduce that it was the wife who was not able to bear kids.

In this week's parasha, the posuk says, “These are the descendants of Yitzchok, the son of Avraham. Avraham was the father of Yitzchok.”

Why the redundancy?

Rashi gives the explanation: It was necessary to say it twice because scoffers of that generation were saying that Sarah conceived by Avimelech, since she lived with Avraham many years and did not conceive by him. So Hashem made Yitzchok's face to look like Avraham's so that everyone would testify that Avraham was the father of Yitzchok.

I've got two questions:

1. What could the scoffers possibly say about Avraham? He had a son with Hagar – Yishmael! Clearly Avrohom was able to have children!
2. If Yitzchok resembled Avraham, then what were the scoffers' claims to begin with? Why would they think Yizchok wasn't the son of Avraham? Father and Son look like each other!

Unfortunately, I was only able to think of an answer to question number two. I remember learning a Gemara in Brachos [20a] which says that Rav Yochanan would sit at the gates of the Women's mikvah. He said, “When women come to the mikvah, they will see me and their seeds [kids] will be as good as I am.”

Rashi in Baba Matziah [87a] says Rav Yochanan was very good looking.

I can infer from the words, “they will see me and their seeds [kids] will be as good as I am,” isn't necessarily talking about physical appearance. It can also mean in kedusha, middos, mitzvos, etc. However, there is a possibility it may also mean physical appearance. I once read (I think in Sefer Chasidim) that if a lady thought or looked at an image of someone else at the time of conception, then her kids will turn out to look like that image.

This can answer my second question; even though Yitzchok looked like Avraham, that doesn't have to mean he is his son. The scoffers could have thought, “Perhaps while Sarah was with Avimelech, she thought of her husband!” Therefore, this may answer why the posuk mentioned Yitzchok ben Avraham twice; to make a point that Yitzchok really was Avraham's son.

If you have an answer to my first question, please email me! I would love to hear it.

Have a wonderful Shabbos,

Nisso

SharingTorah@gmail.com