Parshat Toldot states (25:28), “Vaye’ehav Yitzchak Et Eisav Ki Tzayid BeFiv, VerRvkah Ohevet Et Yaakov,” “And Yitzchak loved Eisav because trapping was in his mouth, and Rivkah loved Yaakov.” Rashi interprets “trapping was in his mouth” to mean that he tricked his father by asking him halachic questions like, “How does one take Maaser from salt [something which is not subject to the Maaser laws]?” This made Yitzchak think that Eisav was careful to keep Mitzvot. However, Rivkah saw through it with ease, as did Yaakov. Why did Yitzchak not realize the trickery of Eisav the Rasha as well? After all, Eisav lived for many years with him – was there not a single instance in which Eisav’s Rish’ut was revealed?
The Maayanah Shel Torah quotes a Peirush explaining that Yitzchak had been brought as a Korban, an offering, and was holier than the average person. He was separated from the world, and he did not even think of the idea that someone could be sly and deceitful. This is why he thought of Eisav as a Tzaddik when he was a Rasha and believed his trickery. Rivkah, on the other hand, grew up in a household of deceivers, including Lavan HaArami, which can be seen as Lavan HaRamai, Lavan the Trickster. She was therefore fully aware of the fact that someone could be a Rasha and at the same time ask questions similar to those who are careful to observe Mitzvot. This is why she opted to love Yaakov instead of Eisav Harasha.
Perhaps this could explain how Rivkah was able to trick Yitzchak so easily into believing Yaakov was Eisav. Rivkah knew that Yitzchak was someone who could be deceived very easily, so she simply dressed Yaakov in Eisav’s clothes and gave him food to give to Yitzchak. However, unlike Eisav’s deception, she used the trickery to attain the firstborn blessing, which Yaakov deserved from the time he purchased it from Eisav, and which he desired for the right reasons, not for evil motives, as Eisav did.
We must learn important lessons learned from Yitzchak and Rivkah. Even though we live in a society where there are some liars and cheaters, we must be like Rivkah in the way that she never lied and cheated in the evil ways her relatives did; we must not give in to pressure and do Aveirot. We must also be aware of the fact that other people will deceive us, and we have to be able to see through it. However, we must also be like Avraham, who was always able to be Dan LeKaf Zechut, to judge people in their favor, and not come to quick conclusions about people and their actions.