Esav held a grudge with Yaakov because of the blessing which his father blessed him; and Esav said in his heart: The days of mourning of my father are drawing near, I will kill Yaakov my brother. It was told to Rivkah the words of Esav her older son; she sent-message and called for Yaakov her younger son, and she said to him: Behold Esav your brother seeks to comfort himself by killing you.
Obviously this raises the question, If Esav “said in his heart,” then who told Rivkah?
Numerous commentators discuss how it is that Rivkah came to know this information. It is claimed that Esav said it aloud to himself, and this is the meaning of “in his heart.” Others propose that he spoke of his intentions to a friend, and the friend informed Rivkah. Yet, our Sages of Blessed Memory have another explanation found in Breishit Rabbah which is also offered by Rashi:
“It was told to Rivkah,” Who told her? Rabbi Haggai said in the name of Rabbi Yitzhak: The Matriarchs were prophetesses and Rivkah was one of the Matriarchs!