The Torah makes Sarah's beauty known.
Genesis 12:11 - And it came to pass, when he was close to
entering Egypt, that he said to Sarai his wife, “Indeed I know that
you are a woman of beautiful countenance.
According to the Midrash, at twenty she still had the beauty of a seven-year-old, and at one hundred she was just as pure from sin as she had been at twenty.
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] [1]
The rabbis questioned why Sarah isn't mentioned in Genesis 12:14, which says, "When Abram entered Egypt." According to the midrashic interpretation, Abraham shut up a chest to try and hide her from the Egyptians.
“It was upon Abram’s arrival in Egypt, the Egyptians saw” – and where
was Sarah? He had placed her in a chest and locked her in it. When
they arrived at customs, they said to him: ‘Pay the duty.’ He said: ‘I
will pay the duty.’ They said to him: ‘[Perhaps] you are transporting
garments?’ He said: ‘I will pay [the duty] for garments.’ They said to
him: ‘[Perhaps] you are transporting gold?’ He said: ‘I will pay [the
duty] for gold.’ They said to him:’ Perhaps you are transporting silk
garments?’ He said: ‘I will pay [the duty] for silk garments.’
‘[Perhaps] you are transporting gems?’ He said: ‘I will pay [the duty]
for gems.’ [Nevertheless,] they said to him: ‘It is not possible [for
you to pass] unless you open [the chest] and show us what is inside
it.’ When he opened it, the entire land of Egypt shone with her radiance.
She was beautiful: The Torah tells us about Sarah’s beauty in several passages. For instance, Genesis 12:11 and the fact that despite her age, Sarah’s beauty was so remarkable that it caught the attention of powerful men like Pharaoh and Abimelech.
Rabbi Ḥanina bar Pappa says that even Abishag the Shunammite was not half as beautiful as Sarah:
She still did not reach half the beauty of Sarah, as it is written:
“Ad me’od,” which can be translated as “up to very fair,” but not
including the praise of “very fair.” By contrast, it is written
concerning Sarah: “She was very fair” (Genesis 12:14).
The Rabbis also say:
Rabbi Bena’a says: I gazed at his, Adam’s, two heels, and they shone
so brightly that they are similar to two suns. Along these lines, the
Gemara states that all people compared to Sarah are like a monkey compared to a human, as Sarah was exceedingly beautiful;
Sarah
compared to Eve is like a monkey compared to a human; Eve compared to
Adam is like a monkey compared to a human; and Adam compared to the
Divine Presence is like a monkey compared to a human.
Rabbi Huna and Rabbi Avun said in the name of Rabbi Meir:
It was so that their husbands could enjoy them, for whenever a woman
carries a fetus, she becomes unsightly and neglected. All ninety years that Sarah did not bear children, she was as [beautiful as] a bride under her wedding canopy.
Sarah had great character: Hebrews 11:11 points out her faith.
By faith Sarah herself also received strength to conceive seed, and
she bore a child when she was past the age, because she judged Him
faithful who had promised.
Furthermore, 1 Peter 3:6 talks about her obedience and respect towards Abraham, which reflects her character.
I believe that Sarah being desired by other men despite her age can also be seen as a testament to God’s favor and protection over her and Abraham.
Conclusion: Sarah was indeed very beautiful; her story is about more than just her physical attractiveness. It’s also about her character, her relationship with God, and the favor of God she enjoyed.