Genesis 23:1

And the life of Sarah was one hundred years and twenty years and seven years: The reason that the word “years” was written after every digit is to tell you that every digit is to be expounded upon individually: when she was one hundred years old, she was like a twenty-year-old regarding sin. Just as a twenty-year-old has not sinned, because she is not liable to punishment, so too when she was one hundred years old, she was without sin. And when she was twenty, she was like a seven-year-old as regards to beauty. — from Gen. Rabbah 58:1]

The years of the life of Sarah: All of them equally good.

And the days of the life of Sarah were an hundred and twenty and seven years, the years of the life of Sarah.

A HUNDRED AND TWENTY YEARS Rashi comments: “The reason the word ‘years’ is written at every term is that it informs you that each term must be interpreted by itself. At the age of one hundred she was as a woman of twenty as regards sin [for at the age of twenty she had not sinned since she had not reached the age when she was subject to punishment], and at the age of twenty she was as beautiful as when she was seven.” Rashi wrote similarly on the verse, the years of Abraham’s life.
However, this exegesis of his is not correct. In the case of the verse, the years of the life of Ishmael, it is stated exactly as in the verse, the years of Abraham’s life, whereas these years of Ishmael were not all equally good since Ishmael was wicked in his early years, and only in the end did he repent of his evil ways. Furthermore, the repetition of the word “year” at every term would seem to indicate an intent to distinguish between them and, thus, should not be interpreted to imply equality. Rather, the use of the word shanah (year) and shanim (years) in this instance is the customary usage of the Hebrew language, while that which the Rabbis have said in Bereshith Rabbah, “At the age of one hundred she was as a woman of twenty as regards sin,” is an interpretation which they derived only from the redundant expression, the years of the life of Sarah, which includes them all and equates them. The Rabbis would not make a similar interpretation of the verse concerning Abraham [since in his case Scripture does not conclude with a similar comprehensive expression].

ויהיו חיי שרה, even though the Torah never revealed the ages of other women, in Sarah’s case it became necessary to inform us of this, as her death was directly related to the purchase of the cave of Machpelah. The Torah therefore told us for how many years Sarah lived after having become a mother at the advanced age of 90.

ויהיו חיי שרה מאה שנה ועשרים שנה ושבע שנים .The Torah repeats the word “year” or “years” three times, even though this verse could have been written using the word שנה only once. We encounter a similar “waste” of the word “year” and “years” in Genesis 6,9 in connection with Noach, as well as in connection with בני ישראל, “the Children of Israel” in Numbers 8,19 where that word occurs no fewer than five times We also find such a repetitive use of the word “year” when we are told about Avraham’s death in Genesis 25,7. Even when reporting the death of Ishmael in Genesis 25,17 the word שנה is repeated three times. Some commentators claim that this is a feature of the Holy Tongue, which endeavours to be clear and unambiguous. When a large number of years (unit) is mentioned the word שנה, “year” appears in the singular mode, whereas when less than ten years are mentioned the years appear in the plural mode, i.e. שנים. There is an aggadic approach to these seemingly superfluous words, especially in our verse here (mentioned by Rashi) which sees in the wording an allusion to the fact that Sarah at her death was as pure and beautiful as at 7 or at 20 years respectively. Seeing that the word שנה did not occur at the beginning of the verse, the verse concludes with the summary שני חיי שרה. When reporting the death of Avraham and Ishmael, seeing that the verses commenced with the words ימי שני, these words are not again repeated at the end of the respective verses. It is possible that in all of these instances the word שני at the end is a hint that the persons concerned lived until the completion of that particular year.

'ויהיו חיי שרה וגו, “the lives of Sarah were, etc.” the description of Sarah having had more than one life must be understood as follows: during the first ninety years of her life she had been childless. Anyone who has no children is really considered as if dead. When you look at the numerical value of the letters in the word ויהיו the total is 37. This is the Torah’s way at showing us that the last thirty seven years of Sarah’s life were really the ones that counted.

חיי שרה, “the lives of Sarah;” according to Rashi all the years that Sarah lived on this earth were equal in the sense that she was a good person during all these years. When we look at the way the Torah describes the years of Yishmael after his death, (Genesis 25,17) the Torah describes them in the same terms, i.e. ואלה שני חיי ישמעאל מאת שנה ושלושים שנה ושבע שנים; does Rashi imply that the Torah compliments Yishmael in the same manner as it complimented Sarah? When we accept that the word ואלה, “and these,” are a hint that he had become a penitent, as Rashi derives from the manner in which his burial is described in the Torah in same verse from the fact that he is described as having been gathered into his forefathers, and we know that a proselyte is considered as if newly born from the day of his conversion, i.e. free from sin, it follows that the years he had lived prior to this have now been converted as a prelude to his conversion, i.e. as part of that conversion process. Another way of explaining the Torah’s wording of the death and burial of Yishmael: the Torah did not preface his death with the unusual words: “and the lives of Sarah were,“ words which alert us that they must have more meaning than the plain text suggests. When Sarah’s death is reported the word חיי, “lives of,” is mentioned twice, not only once. This calls for closer examination. Rashi, therefore was quite correct in alerting his readers to this.