למועד אשוב אליך. מכאן רמז למה שאחז"ל כי בפסח נולד יצחק למוע"ד בגימ' בפסח: למועד אשוב אליך, “at the appointed time I will return to you, etc.” this phrasing is a hint that the birth of Yitzchok would occur on a date subsequently part of the Passover festival. (Talmud tractate Rosh Hashanah folio 11). The numerical value of the letters in the word למועד equals the numerical value of the letters in the word בפסח (150).
כעת חיה. פירש"י כעת הזאת שתהיו חיים לשנה הבאה מדלא קרי בעת חיה ה"א לעת שהאשה יולדת דהיינו לתשעה חדשים וחיה קרי ביה לאשה יולדת כד"א שלש מפתחות לא נמסרו לשליח. של תחיית המתים. של גשמים. ושל חיה. השתא דקרי כעת לאמר שאתם חיים וקיימים. ונ"ל דשטת רש"י כשטת סדר העולם ומכילתא דהכי אתמר התם בט"ו בניסן דבר הקב"ה עם אברהם. בט"ו בניסן באו מלאכי השרת לבשר שרה. בט"ו בניסן נולד יצחק ואמרינן נמי בב"ר לושי ועשי עוגות הדא אמרה שפסח היה וכן משמע בפרשת מילה לעיל דכתיב אשר תלד לך שרה למועד הזה בשנה האחרת אמנם כל זה פליג אדפרק קמא דר"ה דמסיק למועד אשוב אליך דקאי בחג הסוכות וקאמר למועד ראשון שיהיה דהיינו פסח. וגם לפרקי ר' אליעזר דביום הכפורים נמול אברהם אבינו ובפרק השוכר את הפועלים אמרי' דביום השלישי למילתו באו המלאכים אצלו ואז נתבשרה שרה והא דאמרינן בר"ה דקאי בחג ר"ל שני ימים לפני החג. ועוד דבר"ה מסיק נמי בר"ה נפקדה שרה רחל וחנה וזה כשטת רש"י ז"ל דהכא. ואי קשיא לשיטה דהתם מאי למועד הזה בשנה האחרת כיון דבסוכות קאי וקא"ל לפסח א"כ באותה שנה היתה י"ל דסבירא ליה כר' יהושע דאמר בניסן נברא העולם ולהכי קרי פסח שנה אחרת: כעת חיה, according to Rashi, this means “at a time of year such as now, when nature is in full bloom, entirely alive.” Seeing that the angel did not say בעת, at the time, but כעת, “around that time,” it is clear that he referred to the time when Sarah’s pregnancy would result in her giving natural birth at the end of the cycle. She would not give birth prematurely. The expression חיה for a woman giving birth occurs elsewhere also. Our sages in the Talmud tractate Taanit folio 2, have stated that there are three keys which G–d does not hand over to any agent (prophet or angel) They are: the key to resurrections, to rainfall, and to giving birth. This is also why the angel could not predict the precise date when Sarah would give birth, only an approximation, i.e. כעת, “at approximately that time.” I believe that Rashi’s interpretation of these verses coincides with the one we find in the historical text known as Seder olam, world history, as well as with the commentary in the Mechilta. (chapter 5) According to those calculations, G–d had had this conversation with Avraham culminating in the destruction of Sodom on the fifteenth day of Nissan. Yitzchok was born on that day in the year following. According to B’reshit Rabbah 48,12, the words Avraham had used when telling Sarah to knead and bake bread, לושי ועשי עגות, also suggest that it was Passover (the date of) [as did the fact that on the evening of that same day, Lot fed the angels matzot, unleavened bread. (Genesis 19,3) Ed.] This date had also been referred to in conjunction with the circumcision (Genesis 17,21) when G–d had told Avraham about the birth of this son whom he was to call Yitzchok. At that time the time frame told him was: “next year.”
However, the above is in contradiction to what we read in the first chapter of the tractate Roshashah, folio 11, where the words: למועד אשוב אליך are understood to refer to the dates on which the Sukkot festival would occur in the future. The first “מועד” would then have been Passover. This would also agree with what we have read in Pirke de rabbi Eliezer chapter 29, according to which Avraham circumcised himself on the date of the day of Atonement. In the Talmud, tractate Baba Metzia, folio 87, the angels are reported as having visited Avraham on the third day after his circumcision, and that is when Sarah overheard the prediction that she would give birth to a son, and that the words “at this time,” have to be understood as 2 days prior to the date of Sukkot. It is also stated in the Talmud, tractate Rosh Hashanah, that Sarah became pregnant on Rosh Hashanah. When mention is made elsewhere that this occurred on the festival, this need not be understood literally, as it was two days earlier. Furthermore, according to our tradition, also Rachel and Chanah who had endured years of being unable to conceive were remembered by G–d on that festival and became pregnant and subsequently gave birth. This is the version of events accepted by Rashi. If one were to question what precisely was meant by the angel speaking of the מועד in the following year, if it would refer to Sukkot, that would be more than a year later, as the next festival would be Passover in the same year, we must assume that the quotation from the Talmud is by a sage who accepts the opinion of Rabbi Yoshua, that the earth was created in the month of Nissan, (Rosh Hashanah there), in which case Passover would be in the following year and that this is why the angel added words that applied to the following year. [The important thing is that the Torah testifies that Sarah gave birth at the time that been predicted here, compare Genesis 21,2. Ed.]