This week's parsha begins "These are the offspring of Yitzchak ben Avraham; Avraham gave birth to Yitzchak" (Bereishis 25, 19). Rashi enlightens us to the reason behind the pasuk's redundancy. The scoffers in Avraham's generation claimed that Sarah conceived during the night she spent in Avimelech's palace. After all, she was married to Avraham for many years and failed to become pregnant, and shortly after the incident with Avimelech she gave birth to a child. To squelch their claims, Hashem created Yitzchak with a countenance strikingly similar to that of Avraham, which made it clear beyond a doubt that it was Avraham who fathered Yitzchak. Accordingly, the pasuk is to be understood as follows: These are the offspring of Yitzchak, [whom it was clear to all that he was] the son of Avraham since [his facial appearance] bore testimony that Avraham begot Yitzchak.
Rav Wolbe (Shiurei Chumash) comments that it is mindboggling to think about the fact that although Avraham Avinu who was one of the greatest people to ever set foot on earth, nevertheless, there were still scoffers who poked fun at him! The reason behind this phenomenon is rooted in the very creation of the world. Wherever Hashem created holiness He created the converse as well. Every generation has spiritually great men and every generation has the scoffers to counteract the holiness. The Maharal writes that even in the generation of Moshe and Aharon, Dasan and Avirom were there to ensure the spiritual equilibrium. This balance is imperative to facilitate man's free will. If it would be abundantly clear to everyone the integrity and intrinsic goodness of the righteous, there would be no possibility to choose a different way of life. Hence, there are always the scoffers who claim that the righteous aren't as righteous as they seem to be, and their way of life isn't necessarily the proper path to follow.
Our generation is no different in this aspect. There are the righteous and there are the scoffers; and there are those of us who are left in between with the responsibility of utilizing our free will to determine which side is right. Yet, one thing should be abundantly clear. The faction that holds tenaciously to the Torah and mitzvos is the group we are to join and whose lead we are to follow.