Toldot Yaakov Yosef

Regarding the third point: it is stated in the Shas, Berachot, chapter 4 (27b), "Let us appoint Rabbi Elazar ben Azaryah [as head of the yeshiva]." He said, "I will consult with the members of my household," etc., until "You have no white [hair]." A miracle was performed for him, etc. At first glance, this is a wondrous thing.

Here, it seems to me that the matter explained in the Talmud concerning Rabbi Shimon bar Yochai and his son is clear. When they emerged from the cave, they conducted themselves with the attribute of din (strict judgment), and a bat kol (heavenly voice) went forth, saying, "Have you emerged to destroy My world? Return to your cave." After twelve months they emerged with the attribute of rachamim (mercy), and wherever they looked, there was blessing, etc. (Shabbat 33b).

The matter is as the Alshich writes (on Proverbs 3:27), [connecting the verses] "then He will grant you rachamim (mercy)" and "He will show you rachamim" (Deuteronomy 13:18): when the Holy One, blessed be He, wishes to show mercy to a person, it is arranged for him that he perform an act of mercy toward another person, and thereby the attribute of mercy is aroused in the world, etc. — see there.

By this I have explained the passage in the Talmud, Rosh Hashanah (17b), concerning "abundant in chesed (kindness)" and "emet (truth)," which are reconciled, for it is written "abundant in chesed" and it is also written "and emet," etc. — for each person according to his own measure, etc. Even though the difficulty of the Talmud concerns the world in general — how it is that this one arouses chesed and that one arouses emet — understand this.

And this is what his wife said to him, "You have no gray hair" — meaning, that he should enter with the attribute of rachamim (mercy), lest he arouse dinim (judgments) upon himself and upon the world: upon himself, lest they not forgive him, and upon the world, G-d forbid, likewise included, as above. And as soon as he accepted her words, to enter into the level of a zaken (elder) and of rachamim, indeed a miracle was done for him, etc.

And with this one can understand "and Avraham was old, advanced in days" — that "days" represent the aspect of rachamim (mercy), the opposite of "nights," which represent the aspect of din (judgment). Therefore he drew down rachamim (mercy) into the world, and "Hashem blessed Avraham with everything," just as with Rabbi Shimon bar Yochai and his son afterward, when he went out the second time from the cave. And this is readily understood (kal vechomer, by way of a minor point easily grasped).