The תורה tells us that אברהם אבינו lived םישׁ שָׁנ ה וְחָׁמ ים שָׁׁנָׁ ה וְשׁ בְע נָׁ ת שָׁׁ מְא – “100 years, and 70 years, and 5 years”.
רש"י explains that the years are listed this way instead of simply saying that he lived _____ years, because when אברהם was 100 years old he was like one who is 70 years old, and when he was 70 years old he was like one who is 5 years old, without sin.
QUESTION:
רש"י explains that when _______ was 70 years old, he was like a 5 year old, without sin. Why doesn’t רש"י also explain in what way אברהם was like a 70-year-old when he was 100 years old?
ANSWER:
The manner in which אברהם was like a 70-year-old even when he was 100 years old is self-understood from what was already learned __________.
When we learned about the birth of יצחק when אברהם was 100 years old, רש"י explained that although in earlier generations people lived longer and had children later in life, in אברהם’s time this was not so, and people only had children until around the age of 70.
So the very fact that יצחק was born when אברהם was _____ years old already shows us that he was like one who is ___ years old, the oldest age at which others had children, and there is no need for רש"י to explain it again here.
Further discussion:
This also explains why Rashi doesn’t comment on אברהם marring קטורה 40 years after יצחק was born and having 6 more children. How?
(See section 2 in the Sicha)
