Parashat Jayei Sara-Rivka al nivel de Sara

(67) Isaac then brought her into the tent of his mother Sarah, and he took Rebekah as his wife. Isaac loved her, and thus found comfort after his mother’s death.

האהלה שרה אמו INTO HIS MOTHER SARAH’S TENT — He brought her into the tent and she became exactly like his mother Sarah — that is to say, the words signify as much as, [And he brought her into the tent] and, behold, she was Sarah, his mother). For whilst Sarah was living, a light had been burning in the tent from one Sabbath eve to the next, there was always a blessing in the dough (a miraculous increase) and a cloud was always hanging over the tent (as a divine protection), but since her death all these had stopped. However, when Rebecca came, they reappeared” (Genesis Rabbah 60:16).

“Isaac brought her into the tent of his mother Sarah; he took Rebecca, she became his wife, and he loved her, and Isaac was comforted after his mother” (Genesis 24:67).
“Isaac brought her into the tent of his mother Sarah” – all the days that Sarah was alive, there was a cloud suspended over the entrance to her tent. When she died, that cloud ceased. When Rebecca came, the cloud returned. All the days that Sarah was alive, the doors were kept wide open [for guests]. When Sarah died, that opening ceased. When Rebecca came, the opening returned. All the days that Sarah was alive, there was [divine] blessing bestowed upon her dough. When Sarah died, that blessing ceased. When Rebecca came, it returned. All the days that Sarah was alive, there was a lamp kindled from Shabbat night until Shabbat night. When Sarah died, that lamp ceased. When Rebecca came, it returned. When he saw that she was acting just like his mother, separating ḥalla in purity, and shaping loaves from her dough in purity, immediately, he “brought her into the tent.”
Rabbi Yudan said: The Torah teaches you that if an [unmarried] person has adult children, he should see to marrying them off first and then take a wife for himself. From whom do you learn it? From Abraham. First, “Isaac brought her into the tent of his mother Sarah” and then, “Abraham took another wife, and her name was Ketura” (Genesis 25:1).