Midrasch zu Bereschit 49:25

"One such day, he [Yosef] came into the house to do his work and none of the men of the household were there" (Genesis 39:11). Is it possible that in the house of such a man it was deserted with no man there? Rabbi Yehuda and Rabbi Nechemyah [explain this]. Rabbi Yehuda says, it was a Nile festival and all had gone to see it, and he did not go. Rabbi Nechemyah says, it was a day of the theatre [teiatiron] and all had gone to see it, and he did not go. Rather, "he came into the house to do his work", to calculate his master's calculations. Rabbi Shmuel son of Nachman says, "to do his work literally", except there was no man there -- he searched himself, and he did not find himself to be a man. Another explanation, Rabbi Shmuel says, the bow is stretched and returned. For is it not written: (Genesis 49:24) "Yet his bow [קשתו] remained taut" -- his hardness [קשיותו]. Rabbi Yitzchak says, his seed [זרע] was scattered and went out by way of his fingernails, as it says (Genesis 49:24) "and the arms of his hands [זרעי ידיו] were made firm". Rav Huna in the name of Rabbi Matna says, images of his father appeared and chilled his blood, as it is written (Genesis 49:24) "From there, the Shepherd, the Rock of Yisrael". Who does such? (Genesis 49:25) "The God of your father who helps you [...] blessings of breast and womb" -- (Onkelos Genesis 49:25) "blessings of father and mother."