Why Did Avraham Wait Until After Yitzchak (Isaac) Married Rivkah (Rebecca) To Marry Keturah?

IN this week's Parsha we have the story (Breishis 24) of Avraham's servant, Eliezer, finding a wife for Yitzchak. However, what is interesting is the fact that it is only after Yitzchak finds a wife that Avraham marries another woman, Keturah. At the end of Breishis 24 (verse 67) it says:


סז. וַיְבִאֶהָ יִצְחָק הָאֹהֱלָה שָׂרָה אִמּוֹ וַיִּקַּח אֶת רִבְקָה וַתְּהִי לוֹ לְאִשָּׁה וַיֶּאֱהָבֶהָ וַיִּנָּחֵם יִצְחָק אַחֲרֵי אִמּוֹ:
67. And Isaac brought her to the tent of Sarah his mother, and he took Rebecca, and she became his wife, and he loved her. And Isaac was comforted for [the loss of] his mother.

The very next verse (Breishis 25:1) says:

א. וַיֹּסֶף אַבְרָהָם וַיִּקַּח אִשָּׁה וּשְׁמָהּ קְטוּרָה:
1. And Abraham took another wife and her name was Keturah.

The Midrash Tanchuma comments on this (Chayei Sarah 8) and tells us "From here you can learn that if a man's wife dies and he has sons, he should not remarry until he has married his sons off and only then should the father get remarried. [This is learned from Avraham] for he did this after the death of Sarah, he married off Yitzchak (Isaac) and only afterwords remarried." The Midrash Tanchuma goes on to say that it was even Yitzchak's idea that Avraham should remarry. 

I think there is one last piece of the puzzle missing. What is the reason a man should marry of his sons before getting married himself? Is there a halachic reason, psychological reason? What is going on here? 

For this, we bring in the two Rashis on the last verse of Chapter 24. Rashi says:


 האהלה שרה אמו: ויביאה האהלה ונעשית דוגמת שרה אמו, כלומר והרי היא שרה אמו, שכל זמן ששרה קיימת היה נר דלוק מערב שבת לערב שבת, וברכה מצויה בעיסה, וענן קשור על האהל, ומשמתה פסקו, וכשבאת רבקה חזרו
To the tent of Sarah his mother: He brought her to the tent, and behold, she was Sarah his mother; i.e., she became the likeness of Sarah his mother, for as long as Sarah was alive, a candle burned from one Sabbath eve to the next, a blessing was found in the dough, and a cloud was attached to the tent. When she died, these things ceased, and when Rebecca arrived, they resumed (Gen. Rabbah 60:16).    


אחרי אמו: דרך ארץ כל זמן שאמו של אדם קיימת כרוך הוא אצלה, ומשמתה הוא מתנחם באשתו:
For…his mother: It is the way of the world that, as long as a person’s mother is alive, he is attached to her, but as soon as she dies, he finds comfort in his wife. — [Pirkei d’Rabbi Eliezer, ch. 32.]  

The first Rashi, combined with the second Rashi is telling us something very interesting about Yitzchak. Both point to the idea that once Sarah died Yitzchak was upset and in anguish. He could not get over the loss of his mother. This is why the second Rashi tells us that a person is comforted by their wife once their mother dies. However, Yitzchak did not have a wife until now. Also, this is alluded to in the first Rashi when it says the miracles that occurred in Sarah's tent ceased until Rivkah came. The picture here is clear, Yitzchak, like most children, was devastated by his mother's death and, without a wife, could not get over this loss. This is why Avraham, after dealing with the burial of Sarah in Chapter 23, immediately dealt with finding Yitzchak a wife. 

Now, we can understand why it is that Avraham could not get remarried until he found his son a wife. It is not a halacha, but rather an appeal to human emotion. Avraham could have gotten remarried before Yitzchak found a wife. However, Yitzchak had suffered a loss, the greatest loss, of his mother. If Avraham would have remarried without first finding Yitzchak a wife, then Yitzchak would have felt abandoned and uncared for. For, as Rashi points out, what really helps a person get over the loss of a parent is a spouse. There are many other things, but the main comfort is having a support system. This is why it was so important for Avraham to find Yitzchak a wife at this time. 

Rashi also points out that, immediately, after Rivkah entered Sarah's tent that she took the place of Sarah. Why does Rashi say that Rivkah "was Sarah his mother?" because she was now Yitzchak's suport system (like every spouse should be). Sarah was the one to stand up for Yitzchak. For example, she saw Yishmael mistreating Yitzchak and immediately insisted that he be thrown out of the house. Rivkah took over this role. Her assuming this role is best seen when Yitzchak is giving out the blessing. Rivkah wanted to protect Yitzchak and thereby she helped Yaakov trick Yitzchak into giving him the bracha. It was only after this occurred that Yitzchak realize how bad it would have been to give Esau the blessing. This is why, after Yitzchak realizes he gave the bracha to Yaakov, he was trembling in fear, because he almost gave the blessing to the wrong child. If it were not from Rivkah's protection of Yitzchak, then he would have made a grave error. 

The lesson, I think, we can take away from this is the role of a spouse. When a person is growing up they are protected by their parents. Their parents look out for their best interests and help them out. However, when a person finds his or her spouse, the spouse is supposed to assume this role. That is why it is so important to find the right spouse because you must now look after each other like your parents looked after you.