ואברהם ושרה זקנים, "and both Avraham and Sarah were old;⁠" seeing that the Torah tells us in Genesis 24,1 that Avraham was old and advanced in years, what is the point of the Torah telling us here that Avraham was old? The answer must be that in the interval God had restored a degree of youthfulness to Avraham, so that in chapter 24 we are told that by then he had become "old" again. (Compare B'reshit Rabbah 48,16.

זקנים באים בימים, "old advanced in years.⁠" We do not find a single reference to old age in the Torah anywhere before this point. Avraham was the first human being described as having "aged.⁠" The Midrash attributes the fact that the Torah here refers to Avraham's age as due to his having said to God: "with all respect, God, when father and son walk together and come to a town where neither of them is known, how will they know to honour the father, seeing that they both appear as equally youthful? If You were to "crown" elderly people with a visible sign of their being old, they will know to whom to pay their respects first.⁠" God answered Avraham that he had presented a valid argument and that therefore he would be the first human being upon whom this distinction would be bestowed. Along similar lines, the Midrash points out that before Yitzchok, no one was afflicted with physical handicaps, (such as Yitzchok's blindness) Yitzchok was afflicted with such a handicap at his own request, having said to God: "if a human being dies without ever having endured physical handicaps and pain, the attribute of Justice will present a strong case against him by saying that he had never had to suffer any pain for any of the sins he had committed while alive. These pains would have been deemed as punishment so that upon death he could proceed to the regions of eternal bliss in the celestial regions without further delay. God agreed with him, and made him the first human being to be thus afflicted. We have not read about anyone falling sick before Yaakov requested that sickness become part of life on earth. Yaakov argued that unless sickness precedes death, a person would not have an opportunity to allocate his estate to his various beneficiaries. God agreed with him, and thus he became the first person of whom sickness preceding his death is reported in the Torah in Genesis 48,1. The two or tree days that his sickness lasted, gave him an opportunity to arrange his affairs. This is the reason why the Torah informed us that Joseph was given notice that his father was sick. Otherwise, seeing that he had 11 other sons around him in Goshen, why did special notice have to be sent to the capital where Joseph resided? To sum up: Avraham introduced the concept of old age; Yitzchok introduced the concept of people becoming afflicted with serious physical handicaps. Yaakov introduced the concept of sickness due to approaching death.

חדל להיות לשרה אורח כנשים, the Torah emphasizes that although other elderly women had stopped menstruating, Sarah had continued to experience menses, as Rashi has explained on the line; "he took butter and milk,⁠" i.e. that he could not take bread as on that day Sarah had become niddah, had menstruated, thus causing the dough she had handled to become ritually unclean.