Midrash su Genesi 24:60

Rabbi Yehuda said in the name of Rabbi Shimon ben Elazar: Why did Rebecca become barren? It was so the nations of the world would not say: ‘Our prayer produced results,’ as they said to her: “Our sister, may you become thousands and myriads” (Genesis 24:60). This was until Isaac prayed on her behalf, and she was remembered. That is what is written: “Isaac entreated the Lord on behalf of his wife” (Genesis 25:21).
Rabbi Azarya said in the name of Rabbi Ḥanina bar Pappa: Why did the matriarchs become barren? It was so they would not rely on their husbands due to their beauty.¹³³They would not be fully confident in their relationship with their husbands, despite their great beauty, because their husbands would be frustrated by their barrenness. Therefore, they would place their trust in God (Etz Yosef). Rabbi Huna and Rabbi Yirmeya said in the name of Rabbi Ḥiyya bar Abba: Why did the matriarchs become barren? It was so most of the years would elapse without enslavement.¹³⁴In the covenant of the pieces Abraham was told that the four hundred years, beginning with Isaac’s birth, would contain elements of being strangers, enslavement, and oppression (Genesis 15:13). The fact that the matriarchs were barren, together with the fact that the enslavement in Egypt did not begin until after Joseph and his brothers died, ensured that the majority of the four hundred years elapsed without slavery (Etz Yosef). Rabbi Ḥoni [said] in the name of Rabbi Meir: Why did the matriarchs become barren? It was so their husbands would enjoy their beauty, for when a woman becomes pregnant, she becomes ugly and revolting. Know that it is so, as all the years that Sarah our matriarch was barren she would sit in her house like a bride under her wedding canopy. When she became pregnant, her luster was altered, just as it says: “With pain you shall bear children” (Genesis 3:16). Rabbi Levi in the name of Rabbi Shila of the village of Ḥamarta, and Rabbi Ḥelbo in the name of Rabbi Yoḥanan: Why did the matriarchs become barren? It is because the Holy One blessed be He desired to hear their speech. He said to them: ‘My dove, I will tell you why I rendered you barren; it is because I desired to hear your speech.’ That is what is written: “For your voice is pleasant, and your appearance is lovely.”

The servant arose early in the morning and saw the angel standing and waiting for him in the street. He said to them: "Do not hinder me, for the Lord hath prospered my way" (Gen. 24:56). For behold, the man who came with me yesterday, he has prospered my way; behold, he is standing || and waiting for me in the street, as it is said, "And he said to them, Do not hinder me, for the Lord hath prospered my way." They ate and drank at Rebecca's (bridal) banquet. Like a precentor, who is standing and blessing the bride in her bridal canopy, so they stood and blessed Rebecca their sister (wedded) to Isaac, as it is said, "And they blessed Rebecca, and said unto her, Our sister…" (Gen. 24:60).