TT #53 · Parashas Vayeishev · Passuk 39:1
When Yosef was taken down to Egypt, Potiphar, a courtier of Pharaoh and his prefect—an Egyptian—bought him from the Yishmaelim who had brought him there.
Torah Temimah points to Sotah 13b.
“And Potiphar bought him” — Rav said: he bought him for himself [for immoral purposes], and Gavriel came and mutilated him. From where do we know? At first it is written Potiphar, and later Poti-phera.
Derash on the verse (Bavli sugya) — not a formal named middah of the 13. Orthographic shift in the master’s name is read as narrative consequence.
Potiphar’s design on Yosef was blocked; Heaven altered him so that intent could not be fulfilled.