Rebecca immediately disguised Jacob as Esau and had him impersonate Esau before Isaac in order that Jacob be given the blessings. When Esau later returned in order to receive the blessings, Isaac realized what had happened, and acknowledged that Jacob was in fact the more appropriate choice.
The Use of Trickery
וַיֹּאמֶר בָּא אָחִיךָ בְּמִרְמָה וַיִּקַּח בִּרְכָתֶךָ: (בראשית כז:לה)
[Isaac told Esau,] “Your brother came with guile and took your blessing.” Genesis 27:35

The blessings Isaac bestowed upon Jacob were for material prosperity. The fact that Jacob obtained these blessings through cleverness teaches us how we should engage in our own material pursuits. When eating or conducting business, for example, we can appear to be merely tending to our physical needs, similar to the materialistic Esau. But behind this façade, we should really be thinking like Jacob: our true purposes should be spiritual: We should eat in order to have the strength to do good deeds, study the Torah, and observe G‑d’s commandments. We should earn our livelihood in order to have the financial means with which to do all these things, and so on. This is the sort of “duplicity” that we are meant to employ in our interactions with the material world.1