This week's parsha is parshas Toldot, we learn that says that Yitzhak the son of Avraham and Avraham the father of Yitzhak It says in the Midrash when Avraham and Sarah were going to Avi-melech, Avraham told Sarah if they ask you if tell them that you are my sister. Avi-melech took Sarah home for one night and Hashem gave him and everyone in the kingdom Leprosy. Hashem came to Avi-Melech and said you took Sarah the wife of Avraham and that is why you got cursed,  Avi-Melech said but i did not know that Sarah is the wife of Avraham, Hashem said you are right. After one month Sarah became pregnant and the mockers said Avraham and Sarah were married so long and now Sarah is pregnant they said no it might be Avi-Melech's kid but Hashem made it that Avraham and his son Yitzhak were like twins, after a while Avraham asked Hashem that him and his son Yitzhak should not look like each other because when Yitzhak went somewhere people would stand up for him thinking Yitzhak is really Avraham. This is not honer for Avraham. So Hashem made Avraham the first old person. Before this people who where one hundred looked like the age of a twenty years old person. 

Shabbat Shalom! Have a Good Shabbos!