Musar sur Samuel 1 3:3

The fact that Isaac's features reflected those of his father Abraham is pointed out by Rashi on Genesis 25,19. Rebeccah's features were like those of Sarah, as the Zohar points out on Genesis 24,67: ויביאה יצחק האהלה שרה אמו, "Isaac brought her (Rebeccah) into the tent of his mother Sarah." Rabbi Yossi questioned why the Torah did not say לאהל שרה אמו. He explains that the letter ה at the beginning of a word indicates that this was a special tent, the one that contained the Presence of the שכינה. As long as Sarah had been alive, G–d's Presence had never departed from that tent; Sarah had kept a light burning from one Sabbath Eve to the next. This light went out when Sarah died. Now that Rebeccah entered, it began burning again. The reason that the verse mentions Sarah by name, [after all we all know that Isaac's mother was Sarah! Ed.] is to tell us that Rebeccah was like Sarah in all respects. Rabbi Yehudah adds that just as Isaac's features resembled those of his father so much that he was frequently mistaken for Abraham, so Rebeccah's features resembled those of Sarah to such an amazing degree that this had to be emphasized. The Torah points out that Isaac was comforted so as to show us that this was because he had found such a perfect replacement for his mother. The Torah deliberately avoids saying that Isaac was consoled over Sarah's death, but mentions only אחרי אמו, to show that he found continuity. Thus far the Zohar.