Sarah said that Avraham was old. Why did Hashem quote her as having said that she was old?
Ramban, Rashbam, Moshav Zekenim, Da'as Zekenim: "Ani Zakanti" is synonymous with "Acharei Belosi Haysah Li Ednah", so Hashem told the absolute truth. Hashem did hold back a part of the truth - He said "va'Adoni Zakein", and not "va'Ani va'Adoni Zekeinim".
We learn from here that one is permitted to lie for the sake of peace.
Da'as Zekenim: I.e. he does not ejaculate.
Moshav Zekenim, Da'as Zekenim, Hadar Zekenim: We can say that Hashem totally deviated. Sarah saw a sign of returning to her youth (Dam Nidah), but she could not believe that Avraham will be able to father a child.
Why did Hashem take Sarah to task for laughing, but not Avraham, who laughed too?
Moshav Zekenim: Sarah publicized the predicted miracle among her neighbors. It was proper not to fulfill it, for Hashem prefers doing miracles covertly. She then denied (the predicted miracle), for she feared lest (due to the publicity) it not be fulfilled. Avraham prostrated when he heard, amidst gratitude.
Seeing as Sarah did not know that the guests were angels (as the Ramban explained in the previous Pasuk), why did Hashem take her to task?
Ramban: Because she mocked the suggestion that she would have children. She should have believed that it was possible, or have responded with 'Amen!'
Who reprimanded Sarah?