Parashas Vayeira · Passuk 19:33
And they made their father drink wine that night, and the first-born went in and lay with her father, and he did not know when she lay down or when she arose.
Torah Temimah points to Nazir 23a.
TT lemma: בשכבה ובקומה.
English: “When she lay down and when she arose.” It was taught in the name of Rabbi Yosi son of Rav Choni: Why is there a dot over the vav of “uv’kumah” of the first-born? To teach that when she lay down he did not know, but when she arose he did know.
Derash on the verse (Bavli / dotted letters) — not a formal named middah of the 13. The masoretic dots signal a difference in knowledge.
Lot was unaware when the first-born lay down, but he became aware when she arose; the dotted letter marks that distinction.