Genèse 18:13

And I am old. The Scripture changed it for peace, for she said: "And my husband is old".

And the Lord said to Abraham, Why hath Sarah so laughed, saying, Can it be in truth that I shall bear, being old?

I BEING OLD. This is the explanation of Sarah’s words, after I am waxed old. And G-d’s words [that Sarah had said, “I being old“], were true, but for the sake of peace He did not reveal what she also said, namely, My lord being old also, for [if He were quoting Sarah], He should have said, “I and my lord are old,” as Sarah had laughed concerning both of them.

'ויאמר ה, the angel, the senior of the three.

ואני זקנתי, for she had referred to her menopause in verse12.

'ויאמר ה, the angel is accorded the name of his Master, something that we find also in connection with Gideon in Judges 6,16.

?האף אמנם אלד, will such a miracle indeed occur on my behalf even though I am that old? Even though the angel did not answer her point by point, he did answer her with an overall statement that there simply is nothing which is beyond G’d’s power to accomplish if he so desires. Our author uses a similar approach when examining the words Eliezer used in explaining his mission in Genesis 24,39. There too, the fact that he conveyed the content of what he had asked Avraham before undertaking his mission was important, the exact wording was not the issue. The angel did not even bother to reply to Sarah’s statement that her husband too was too old to impregnate her with semen. The reason he did not do so was that Sarah having had her menopause was the far greater natural impediment to her becoming pregnant. It is not altogether unknown for old men to father children even in their advanced old age.

ואני זקנתי, “and I am old.” Our sages base their view that it is permissible sometimes to tell a “white” lie when the purpose is to preserve harmony between husband and wife, based on this verse, where what Sarah obviously meant was that her husband was too old to sire a child, seeing that she herself had experienced rejuvenation. (Talmud, tractate Baba Metzia folio 87). Seeing that she had not said anything aloud about what she thought about her husband, G–d, i.e. His angel, still saw fit to change what she had thought to herself, in order to preserve her image as a dutiful wife respecting her husband’s masculine dignity. Our author bases his interpretation on the use of the word היתה, “was,” instead of תהיה, “will be,” in verse 12. There is however an opinion which does not agree at all that G–d or His angel had changed the words that Sarah had thought but not uttered. It argues that it is totally absurd to argue that anything appearing to us as a lie could have been uttered by G–d or His agent, an angel. The author of that opinion quotes Psalms 101,7: דבר שקרים לא יכון לנגד עיני, “he who speaks untruths shall not stand before My eyes,” in support of his statement. He claims further that what Sarah had (thought) reported as having said was indeed what is quoted by the Torah, i.e. ואני זקנתי, “and I have become old.” These words are to be understood as her wonderment at how she could have become pregnant even in spite of having seen menstrual blood once more, seeing she was way beyond child-bearing age, and had never previously conceived. The angel did not alter her words, he only did not report all of her words. In this manner he prevented any bad feeling on the part of Avraham. Any ordinary person, other than a Divine creature, is permitted to tell white lies in order to preserve שלום בית, family harmony. If you were to argue that Avraham would not have cared, seeing that he was aware that what she thought or said was true, we must assume that he was still trying to impregnate Sarah but had been unsuccessful.