תלמוד בבלי מסכת סוטה דף יג עמוד א
ומנין היה יודע משה רבינו היכן יוסף קבור? אמרו: סרח בת אשר נשתיירה מאותו הדור, הלך משה אצלה, אמר לה: כלום את יודעת היכן יוסף קבור? אמרה לו: ארון של מתכת עשו לו מצרים וקבעוהו בנילוס הנהר, כדי שיתברכו מימיו. הלך משה ועמד על שפת נילוס, אמר לו: יוסף, יוסף, הגיע העת שנשבע הקדוש ברוך הוא שאני גואל אתכם, והגיעה השבועה שהשבעת את ישראל, אם אתה מראה עצמך - מוטב, אם לאו - הרי אנו מנוקין משבועתך, מיד צף ארונו של יוסף.
Talmud Bavli, Sotah, 13a
How did Moshe know where Yosef was buried? They said: “Serach bat Asher remains from that generation.” Moshe went to her and said: “Do you know where Yosef is buried?” She said: “The Egyptians buried him in an iron casket and placed it in the Nile so that its waters become blessed.” Moshe went and stood at the banks of the Nile. He said: “Yosef, Yosef, the time has come that the Holy One, blessed be He, swore that He would redeem them. The time has also come for the oath that Israel swore (to bury Yosef in the land of Israel). If you show yourself, well and good. If not, we are free from your oath.” Immediately, Yosef’s casket floated to the surface.
The tradition of Serah’s immortality is also reflected in a narrative set in the time of the Rabbis, in which Serah appears in order to resolve a disagreement in the academy (bet-midrash). R. Johanan was sitting in the bet-midrash and expounding the verse (Ex. 14:22): “the waters forming a wall for them on their right and on their left.” How could the water become as a wall? R. Johanan expounded that it was a sort of [impervious] net. Serah appeared and said: “I was there, and the water was not as a net, but as transparent windows” (Pesikta de-Rav Kahana 11:13). In this midrashic vignette, Serah is an extremely old woman who can testify, in the first person, to the miracle of the parting of the Reed Sea. In her wisdom, she is capable of comprehending, and participating in, the aggadic discussion conducted in the bet-midrash. Her statement is preferred to that of R. Johanan, since she has first-hand knowledge of the facts.