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Even after learning of his brother's deceit Esau cries out to his father for blessings as well never mentioning any reprisals.

We are only told that he planned murder in his heart and there is no record of him telling anyone.

Genesis 27

[41]So Esau bore a grudge against Jacob because of the blessing with which his father had blessed him; and Esau said to himself, "The days of mourning for my father are near; then I will kill my brother Jacob."

But later we are told Rebekah knew of Esau's plan

Genesis 27

[42]Now when the words of her elder son Esau were reported to Rebekah, she sent and called her younger son Jacob, and said to him, "Behold your brother Esau is consoling himself concerning you by planning to kill you.

How did Rebekah know about Esau's plan?

We are not told how Rebecca found out about Esau's plot, for three reasons, in order of importance:

1. The point of the narrative is to show Rebecca's craftiness and foresight


2. It would distract from the focus on Jacob and Rebecca


3. The agency of her knowledge doesn't matter

The first point of the narrative is to show Rebecca's resourcefulness and craftiness, true to her family tradition, and to contrast this with Jacob's placid nature. She hatched a plot, and now she shows that she has the foresight and wits to deal with the consequences, while Jacob does not see the consequences coming.

If we were told who told her, the narrative would have to deal with that fact, which would be extraneous and a distraction.

It doesn't matter. By omitting this detail the narrative is telling us that whether by prophecy, angels, hearsay, paid informants or deduction, she was effective in finding out Esau's intentions and taking appropriate action.

In the continuation of the story we are shown how it takes Jacob more than fourteen years with his crafty uncle Laban in Haran to learn these same skills himself, which earns him the blessing of the angel at the Jabbok gulch, enables him to confront his brother, and be worthy of returning to inherit the lands promised to his fathers.

What is left out of the narrative is sometimes as important as what is written.

I agree with @Abu Munir Ibn Ibrahim. However, the text in Gen 27:42 provides a clue. While we are (importantly) not told how Rebecca learned of Esau's revenge plans, it is recorded that she was told.

"When Rebekah was told what her older son Esau had said, … "

That is, he had either told someone else (perhaps a household servant or a friend?) who then reported it to Rebecca, or, someone overheard him telling someone who then reported it to Rebecca. Either way, she was told what Esau had said.

My view on these things is simple - if the text does not reveal some detail and it cannot be deduced from other surrounding material, then it is not important to know - I am too busy with what has been revealed to be overly concerned by what is not revealed.