English: Just as they [the righteous] are perfect, so their years are perfect: at twenty she was like a seven-year-old in beauty; at one hundred she was like a twenty-year-old with regard to sin.
On the daf / in context: The repeated word “year” after each numeral is taken to teach that each stage of Sarah’s life is evaluated on its own: sinless at one hundred as at twenty, and beautiful at twenty as at seven.
Type of Learning
Derash on the verse (midrash aggadah) — not a formal named middah of the 13: the repeated “shanah” is read as requiring separate evaluation of each age-band.
What Is Learned
Sarah’s years are described as perfect: free of sin at one hundred as at twenty, and of the beauty of a child at twenty; each stage of her life stands complete in its own right.