וַתִּהְיֶ֖יןָ מֹ֣רַת ר֑וּחַ לְיִצְחָ֖ק וּלְרִבְקָֽה׃ (ס)
און זײ זײַנען געװען אַ האַרצביטערניש פֿאַר יצחקן און פֿאַר רבקהן.
Rashi
מרת רוח [AND THEY WERE] A VEXATION OF SPIRIT — the expression means opposing the spirit of a person. The first word is of the same root as (Deuteronomy 9:24), “Ye have been rebellious (ממרים)”: all their actions tended to be a grief
Chizkuni
ותהיין מורת רוח, “both of these daughtersinlaw became sources of frustration to both Yitzchok and Rivkah. We see this from Rivkah’s justifying her wishing to take a wife from her family (27,46) by telling her husband that if Yaakov were to take wife from the local Hittite population she would get fed up with her very life. What can describe more graphically her and her husband’s frustration at the choice of wives Esau had made? Moreover, it is likely that if these daughtersinlaw had been compatible with them they would all of them have lived in one house. The fact that they did not live under one roof is clear, as Yaakov would never have gotten away with deceiving his father by pretending to be Esau if Esau’s wives had lived in the same house! He had expelled them from his house on account of their conduct. [I find this argument very weak, as in Genesis 2,24 already the Torah describes a son marrying and setting up house for himself and his wife as being the norm and not the exception. Ed.]
Rashbam
ויקח אשה את יהודית....ותהיין מורת אוח, seeing that Rivkah is reported in 27,46 as becoming fed up with her life if she would have to live to see Yaakov also marry a Canaanite girl, the Torah had to explain what had produced such a prejudice in Rivkah against the local girls.
מורת רוח, the construction of the word מורת, with the vowel patach under the letter ר needs to be understood by comparing it to the root עשה, also a root ending with the letter ה. In Psalms 148,8 we have the formulation ossah devaro, which is feminine, seeing it describes the activity of the רוח סערה, a stormy wind, which is feminine. The construct form of the word ossah there would be ossat, Similarly, the word מורת in our verse is a construct form of the feminine form of the word מורה, not with the vowel segol under the letter ר but with the vowel kametz. [as in numerous similar nouns that appear sometimes as feminine and sometimes as masculine. Ed.] The word מורה meaning being contrary, rebellious, also appears in a slightly different form, i.e. ממרה as for instance, in Joshua 1,18 ימרה את פיך, “someone who will rebel against your orders.” When it appears in a genitive, construct form, it becomes morat. In Proverbs 14,10 we encounter a similar construction (though it is written with the vowel kametz under the letter מ) The verse reads: אבל לב יודעת מרת נפשו, “a heart knows its soul’s bitterness.” The use of the chataf kametz under the letter מ there converts the word from adjective to being a noun. It is derived from מררות, “something bitter.” (compare Deuteronomy 32,32) In our verse here the word מורת is not a noun but a construct form of a verb, similar to Lamentations 1,20 כי מרה מריתי, “for I am experiencing a great deal of distress.” Here (in our verse) the vowel cholem instead of kametz as in Lamentations, is a manifestation of the abbreviated, chataf vowel often found with the middle letter of the root
מורת רוח, the construction of the word מורת, with the vowel patach under the letter ר needs to be understood by comparing it to the root עשה, also a root ending with the letter ה. In Psalms 148,8 we have the formulation ossah devaro, which is feminine, seeing it describes the activity of the רוח סערה, a stormy wind, which is feminine. The construct form of the word ossah there would be ossat, Similarly, the word מורת in our verse is a construct form of the feminine form of the word מורה, not with the vowel segol under the letter ר but with the vowel kametz. [as in numerous similar nouns that appear sometimes as feminine and sometimes as masculine. Ed.] The word מורה meaning being contrary, rebellious, also appears in a slightly different form, i.e. ממרה as for instance, in Joshua 1,18 ימרה את פיך, “someone who will rebel against your orders.” When it appears in a genitive, construct form, it becomes morat. In Proverbs 14,10 we encounter a similar construction (though it is written with the vowel kametz under the letter מ) The verse reads: אבל לב יודעת מרת נפשו, “a heart knows its soul’s bitterness.” The use of the chataf kametz under the letter מ there converts the word from adjective to being a noun. It is derived from מררות, “something bitter.” (compare Deuteronomy 32,32) In our verse here the word מורת is not a noun but a construct form of a verb, similar to Lamentations 1,20 כי מרה מריתי, “for I am experiencing a great deal of distress.” Here (in our verse) the vowel cholem instead of kametz as in Lamentations, is a manifestation of the abbreviated, chataf vowel often found with the middle letter of the root