Midrasz do Samuela I 17:36

It is written: “And set it in the ears of Joshua” (Exodus 17:14), this is one of four righteous people to whom a portent was given; two sensed it and two did not sense it. A portent was given to Moses, but he did not sense it. A portent was given to Jacob, but he did not sense it. A portent was given to David and Mordekhai, and they sensed it.
Jacob – the Holy One blessed be He said to him: “I will protect you wherever you go” (Genesis 28:15), and he was frightened. A person to whom the Holy One blessed be He made a promise was frightened, as it is written: “He was frightened” (Genesis 32:8)? Rather, he said: Perhaps when I was in the house of Laban the impure, I became sullied with impurity.
Moses – “and set it in the ears of Joshua,” indicating that Joshua will lead Israel into the land. And it is written: “I pleaded with the Lord [… please let me cross over and see the good land on the other side of the Jordan]” (Deuteronomy 3:23-25).
However, David and Mordekhai were given a portent and they sensed it. David said: “Your servant has smitten both the lion and the bear” (I Samuel 17:36). David said: Am I so important that I was able to smite these wild beasts? Rather, he said: Perhaps an event is destined to befall Israel, and they are destined to be rescued by me.
Mordekhai – “Mordekhai would walk before the courtyard of the harem” (Esther 2:11). He said: Is it possible that this righteous one [Esther] will mary an uncircumcised man? Rather, a great event is destined to befall Israel and they are destined to be rescued by her.

10) This tells me only of (offering) offspring and substitutes of whole animals. Whence do I derive the same for the offspring and substitutes of blemished animals? From "whether male" — to include the offspring of blemished animals; "whether female" — to include the substitutes of blemished animals. Which are considered blemished animals (in this connection)? Those whose consecration preceded their blemish (and which gave birth before they were redeemed). But if their blemish preceded their consecration and they were redeemed, they have the status of property consecration (and not body consecration; their offspring are permitted for mundane purposes, and they are not susceptible of a "substitute"). R. Yehudah says: (Similarly,) it is written (I Samuel 17:36): "Also the lion, also the bear, did your servant smite." This tells me only of the lion and the bear. Whence do I derive (that he smote) their whelps, too? From "also the lion, also the bear, did your servant smite."

(reversion to what precedes:) Jacob was given a hint and he did not take it, it being written (Genesis 28:15) "And, behold, I am with you, and I shall keep you wherever you go," yet he was frightened and he feared, as it is written (Ibid. 32:8) "And Jacob feared greatly and he was distressed." A man whom the Holy One Blessed be He had assured feared and was frightened? (How can that be?) Our father Jacob thought: Woe unto me; perhaps my sins will cause (the abrogation of the assurance.) David was given a hint and he took it, viz. (I Samuel 17:36) "Both the lion and the bear has your servant slain." Why then should I fear (Goliath, I) who have killed these (other) wild beasts? It must be that something is destined to transpire in Israel and that they are destined to be saved by me! Mordechai was given a hint and he took it, viz. (Esther 2:11) "And every day Mordechai would walk in the courtyard of the harem, etc.": He said: Is it conceivable that this righteous one (Esther) is to marry this uncircumcised one (Achashverosh)! It must be that something (momentous) is in store for the Jews, and that they are destined to be redeemed through her.

David and Mordecai were given signs and took cognizance of their meaning. To David: He said: Thy servant smote both the lion and the bear (I Sam. 17:34), and to Mordecai: And Mordecai walked every day before the court of the women’s house, etc. (Est. 2:11). Mordecai had said to himself: Perhaps this righteous woman is to marry this uncircumcised man in anticipation of some momentous event that will occur to Israel in the future. And ultimately Israel was saved through her.