Мидраш к Берешит 23:1

(Gen. 23:1:) NOW < THE LENGTH OF > SARAH'S LIFE WAS < A HUNDRED AND TWENTY-SEVEN YEARS >. (Gen. 24:1:) NOW ABRAHAM WAS OLD, WELL ALONG IN YEARS. This text is related (to Ps. 5:13 [12]): FOR YOU BLESS THE RIGHTEOUS ONE, < O LORD, ENCOMPASSING HIM WITH FAVOR AS WITH A BUCKLER >. From when the world was created until Abraham arose, the Holy One would bless his world. So, when he had created Adam and Eve, he blessed them, as stated (in Gen. 1:28): AND GOD BLESSED THEM…. He blessed Noah and his children, as stated (in Gen. 9:1): THEN GOD BLESSED NOAH AND HIS CHILDREN. When Abraham arose, he made him a father for all creatures,¹Buber suggests emending “creatures” to “blessings.” as stated (in Gen. 12:2f): AND YOU ARE TO BE A BLESSING…. < FOR IN YOU SHALL ALL THE FAMILIES OF THE EARTH BE BLESSED >. Ergo (in Ps. 5:13 [12]): FOR YOU BLESS THE RIGHTEOUS ONE (i.e., Abraham), O LORD, ENCOMPASSING HIM WITH FAVOR AS WITH A BUCKLER, in that the Holy One became like a shield for him, as stated (in Gen. 15:1): I AM YOUR SHIELD. Now a buckler is nothing but a shield, as shown in the verse (I Sam. 17:7): AND THE ONE BEARING THE BUCKLER WAS GOING BEFORE HIM (i.e., Goliath). What is the meaning of ENCOMPASSING HIM WITH FAVOR? That he blessed Abraham in his old age, as stated (in Gen. 24:1): NOW ABRAHAM WAS OLD.

As it was taught; And the life of Sarah....

When she was 100, she was like 20 in sin, and when she was 20 she was like a 7 year old in beauty. Therefore, they said 100 and 20 and 7 years.