Two dangerous things are said, one by Jacob and one by Rachel, which foretell or cause a tragedy.
First Rachel blames Jacob for her barrenness, rather than praying to Gd. Very dramatically she states:
When Rachel saw that she had borne Jacob no children, she became envious of her sister; and Rachel said to Jacob, “Give me children, or I shall die.”
Jacob answered Laban, saying, “I was afraid because I thought you would take your daughters from me by force.
עִ֠ם אֲשֶׁ֨ר תִּמְצָ֣א אֶת־אֱלֹהֶיךָ֮ לֹ֣א יִֽחְיֶה֒ נֶ֣גֶד אַחֵ֧ינוּ הַֽכֶּר־לְךָ֛ מָ֥ה עִמָּדִ֖י וְקַֽח־לָ֑ךְ וְלֹֽא־יָדַ֣ע יַעֲקֹ֔ב כִּ֥י רָחֵ֖ל גְּנָבָֽתַם׃
But anyone with whom you find your gods shall not remain alive! In the presence of our kinsmen, point out what I have of yours and take it.” Jacob, of course, did not know that Rachel had stolen them.
Every word has power, and I also see shadows of Rachel's threat in the failures of her descendant King Saul. Contrast Rachel and the names she gave her children with her sister Leah, who recognized Gd's power in the names she gave her children. King David is clearly her descendant and the leader most fitting to lead the Jewish People and produce the Moshiach.
*Judges 11וַיִּדַּ֨ר יִפְתָּ֥ח נֶ֛דֶר לַיהוָ֖ה וַיֹּאמַ֑ר אִם־נָת֥וֹן תִּתֵּ֛ן אֶת־בְּנֵ֥י עַמּ֖וֹן בְּיָדִֽי׃
And Jephthah made the following vow to the LORD: “If you deliver the Ammonites into my hands,
וְהָיָ֣ה הַיּוֹצֵ֗א אֲשֶׁ֨ר יֵצֵ֜א מִדַּלְתֵ֤י בֵיתִי֙ לִקְרָאתִ֔י בְּשׁוּבִ֥י בְשָׁל֖וֹם מִבְּנֵ֣י עַמּ֑וֹן וְהָיָה֙ לַֽיהוָ֔ה וְהַעֲלִיתִ֖הוּ עוֹלָֽה׃ (פ)
then whatever comes out of the door of my house to meet me on my safe return from the Ammonites shall be the LORD’s and shall be offered by me as a burnt offering.”